THE ABORTION
OF THE
YOUNG
STEAM ENGINEER'S GUIDE
CONTAINING
|
An investigation of the principles,
construction and powers of Steam Engines. |
A description of a Machine, and its
principles, for making Ice and cooling water in large quantities, in hot
countries, to make it palatable and wholesome for drinking, by the power of
Steam: invented by the author. |
ILLUSTRATED WITH FIVE ENGRAVINGS
BY
OLIVER EVANS, OF PHILADELPHIA,
AUTHOR OF
THE YOUNG MILLWRIGHT AND MILLER'S GUIDE
PHILADELPHIA:
PRINTED FOR THE AUTHOR BY
FRY AND KAMMERER
. . . . . . . . .
1805
Ed. Downloaded from
the U. of Rochester Steam Collection (http://www.history.rochester.edu/steam/brown), some
corrections and additions made based on the original text. (The Appendix is not
well transcribed and corrections are not possible.) JMcV., May 2008
CONTENTS.
ARTICLE II. Comparison of the powers of the old and new
principle
ARTICLE
V. Of the construction of boilers, A table of the diameters and strengths of
boilers
ARTICLE
VI. Of the means of applying steam, A table showing the proper time to shut off
the steam,
ARTICLE
VII. Comparison of the principles
ARTICLE
VIII. Of the Supply-pump
ARTICLE
X. Of the volcanic Steam Engine,
ARTICLE
XV. Of vibrating motions of machinery
ARTICLE
XVI. Description of a steam engine on the new principle. Explanation of Plate I
ARTICLE
XVII. Explanation of the screw mill invented by the author
ARTICLE
XVIII. Useful inventions by different persons
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About The Hopkin Thomas Project
Rev. January 2011
THE Steam Engine, of which the principles are
described in this work, may be suited to every purpose for which power is
wanted. To apply it to drive mill-stones one cog-wheel on the shaft of the
fly-wheel, geared into the trundle, will give the stone its proper motion. To
saw timber one cog-wheel on the shaft of the fly, geared into a pinion on the
crank of the saw, gives it motion; or, more simply, the saw and engine may both
be attached to the crank of the fly, which in this case is made a double crank,
and the engine made to strike as quick as the saw; for it will strike, as may
be required, from 10 to 100 strokes per minute. To pump water the pump-rod may
be attached to the same crank. To press the juice out of sugar canes one small
pinion on the fly, gearing in a cog-wheel on the middle roller, gives the mill
its proper motion. To work a rolling-mill, the rollers may be simply attached
to the shaft of the fly. To work a forge-hammer the shaft of the fly may be
made to lift the hammer; furnace bellows may simply be attached to the crank of
the fly, and the flue of the furnace conducted under the boiler to drive the
engine by the heat of the furnace. To propel a boat against the stream the
paddle-wheel may be attached to the shaft of the fly-wheel, and the motion may
be regulated by increasing or decreasing the motion of the engine. For this
purpose this engine will answer better than any other steam engine heretofore
used, because its power is five times as great in proportion to its weight and
size, and the power may be augmented to a great degree and kept in reserve to
ascend the most rapid currents. It will answer well to drive a land carriage
with a heavy burden, because the engine and fuel will not make one-eighth of
the load. A pinion on the shaft of the fly to gear into a , which is fixed on
the axle of the two wheels, will give them motion forward or backward at
pleasure, and enable the engineer to turn his carriage on a small space of
ground. To raise coals and water out of mines it will also answer well. The shaft
of the fly- wheel may wind the ropes to raise one bucket while the other
descends; and as soon as the loaded bucket is up the engine may be made to stop
of itself, empty the bucket and turn the other way to raise the other, and so
on alternately; as it will turn either way with equal convenience, and pump
water all the while.
In
the performance of all work that can afford the labour of men and horses, and
to which the engine will apply, it will make, clear of all expenses, at least
one dollar for every bushel of coals it burns, and more, even supposing the
coals to cost forty cents per bushel. An engine that would cost 4 or 5000
dollars, will saw 6 or 8000 feet of boards in 12 hours, or grind 4 or 500
bushels of wheat in 24 hours, and clear 100 dollars per day in some parts of
this country.
To
chop grain and pump for distilleries and breweries, a very small engine will
answer. The heat of the fire, after it leaves the engine with the steam, may be
applied to heat the mashing tubs, &C and thus the fire may be made to
answer a double purpose. In paper-mills the steam engine may be employed with
peculiar advantage; the power to cut, clean and grind the rags and work the
screws of the presses; and the steam to heat the vats. For turning-lathes and grind-stones,
a very small and cheap engine will answer.
Persons
desirous of procuring steam engines on the principles described in this work,
may be supplied with them suitable for any of the above purposes by applying to
the patentee. Any infringement of his exclusive right will be treated as -the
act of Congress in such cases directs.
OF STEAM.
OF all the principles of Nature, which man by
his ingenuity has yet been able to apply as a powerful agent to aid him in the
attainment of a comfortable subsistence, Steam, produced by boiling water, will
perhaps soon be esteemed first in the class of the most useful for working all
kinds of mills, pumps, and other machinery, great or small.
Water-falls are not at our command in all places,
and are liable to be obstructed by frost, drought, and niany other accidents.
Wind is inconstant and unsteady:animal power, expensive, tedious in the
operation, and
unprofitable, as well as subject to innumerable
accidents. On neither of these can we rely with certainty. But steam at once
presents us with a faithful servant, at command in all places, in all seasons;
whose power is unlimited; for whom no task is too great nor yet too small;
quick as lightning in operation; docile as the elephant led by a silken thread,
ready, at our command, to rend asunder the strongest works made by the art of
man.
In our search for the means to apply this agent,
we have wandered from the true path of nature. It has long been known, that
steam confined would in all cases burst the vessel if a sufficient degree of
heat were applied, and no vent given for it to escape; and it was equally well
known, that if it had liberty to escape, no heat that we could apply would
endanger the bursting of the vessel. Was there ever a plainer case presented to
our view in all the works of nature, or an inference more easily drawn, than
that by this agent we can obtain any power we may want, by the simple means of
confining the steam and increasing the heat? or that to do this we had only to
make our boilers strong in proportion to the power we wished to obtain. Yet
philosophers have immortalized their names by wandering from this simple path
of nature, leading the world astray to stumble in the dark for one hundred
years, over the many obstacles which lay in the crooked way; by discovenng that
steam might be used as an agent to drive the air out of a vessel, and that this
steam could be instantly condensed again by a jet of cold water, and by these
means form a vacuum in the vessel, that the air under the weight of the
atmosphere, being suffered to rush into the vessel, would produce a power
sufficient to work an engine. This was certainly a great discovery, and will
ever remain useful; and being improved on, finally produced the greatest and
most powerful engines ever invented by human ingenuity.*
*Here
the reader should know, that the weight of the atmosphere (which is the air
surrounding the earth), has been found to be equal to 15 pounds to every
superficial inch of the area of the whole surface of the earth. This air, being
so heavily pressed by its own weight, insinuates itself into the cavities of
all bodies; and inside as well as outside of all animals which move therein.
They are insensible of the pressure, because the elastic spring of the air
inside their bodies is exactly equal to its weight outside, and instead of
pressing them to the earth it buoys up a part of their weight, the same as any
other fluid does, in proportion to its weight, when they walk in it. When we
walk in water we can hardly sink to touch the bottom, because the water is of
greater specific gravity than our bodies. Balloons rise in air because they are
lighter than their bulk of air: our bodies would sink but little in
quicksilver. If we by any means extract the air from the inside of a vessel we
form what is called a vacuum, there being no air inside to balance, by its
elastic spring, the weight outside of the vessel, every inch of its surface
being pressed inward by a weight equal to 15 pounds. Steam, let into a cylinder
in which a piston is fitted to work, drives out the air, and the steam being
condensed by a jet of cold water, forms a vacuum under the piston, and the
weight of the air on the upper side presses the piston to the other end of the
cylinder, with a power equal to 15 pounds to the inch of its area: thus steam
has been used as the best means for forming vacua to apply the weight of the
air as a power to move 3
To philosophy we are indebted for many our most
useful discoveries; yet this since case should put our philosophy to the blush,
and teach us, however learned we may be, to listen with thc closest attention,
even to what the most illiterate mechanician, who has taken the simple works of
nature for his guide, may say. He would have pointed out to us, that it is much
easier to apply the elastic power of steam simply to work the engine in the
first instance. But we have shut our ears, and continue to use arguments to
prove the application ot the simple principle impossible, even after it is applied
to engines daily in operation before our eyes.
COMPARISON OF THE
POWERS OF THE OLD AND NEW PRINCIPLES.
ON the principle of using the steam as an agent
to form a vacuum, the power of the engine has never been made to exceed 12 or
15 pounds to the inch area of the piston. The vacuum being imperfect in all
cases, the practice falls short of the theory; and the boilers being
constructed of such form, as to be only sufficient to bear a power of steam,
necessary as the agent, a little exceeding the weight of the atmosphere,* were
subject to be blown up by overloading the safety valve; the load allotted being
3 pounds to the inch, it is very easy to double it to 6 or 12 pounds, by
accident, when, if the steam does not get vent, the boiler explodes.
But on the new principle of working simply by
the elastic power of the steam, the power may be raised with safety, from 12 to
120 pounds to the inch area of the piston, which makes this engine ten times as
powerful as the other, and because the boilers are constructed of circular
forms, (the best possible form for holding a great elastic power,) and so as to
bear from ten to forty times the load that is generally required on the safety
valve, which is not subject to be laid on by accident, this engine is by far
the safest.
*When
we speak of steam equal in power to the weight of the atmosphere (which we call
atmospheric steam) we mean, steam produced by the boiling heat under the
pressure of the atmosphere. 212 degrees, the boiling heat of water-170 degrees,
the boiling heat of spirits of wine.
ON SAVING FUEL, AND
INCREASING POWER, BY THE NEW AND
SIMPLE PRINCIPLE.
A QUESTION naturally arises; what proportionate
increase of fuel is required to increase the power? It has been generally
supposed, that double fuel was requisite to produce double elastic power, and
keep it up to work an engine; and consequently nothing was to be gained on that
principle. Yet, had we closely observed the works of nature, how rapidly the
power must increase to produce the effects we have often seen, we would readily
have drawn another conclusion.*
*If
a bottle of water tightly corked be set near the fire, the cork will presently
fly out, or the bottle will burst with a loud report. Put half a gill of water
into a musket barrel, ram a tight wad strongly down, put the barrel into a
fire, and it will shoot with a force and report equal to powder. A coppersmith
made a strong globular but small vessel for one of his customers, who next day
came with the appearance of one just escaped from the grasp of death, to relate
that he had filled the vessel with water, set it on the fire, and that after
some time it exploded with the noise of a cannon; that he had narrowly escaped
with life, and was determined never to try another experiment on the power of
steam. Other accidents more tragical might be mentioned. But shall we refuse to
use as much power as we want because we can increase it to a dangerous degree?
Observing the principles of nature, in the
production of such accidental effects as before stated, I, in the year 1784,
conceived the principles and arranged the means of working steam engines with a
power equal to 10 atmospheres, and applied, in 1786, to the legislature of
Pennsylvania for the exclusive right of propelling land carriages by steam in
that state, for twenty-one years; but they conceived me to be deranged, because
I spoke of what they thought impossible, and refused. I applied next to the
legislature of Maryland, who granted me the exclusive right for fourteen years,
because, said they, it can injure no man and may cause him to produce something
useful. This term I conceived to be too short; the grant however, had the
effect to prevent me from relinquishing my studies on steam: time will shew the
better policy of the legislature of Maryland in this case.
I cannot suppose that any person, who
understands the principles of mechanics, after having seen a rocket rise into
the air by the reaction of its fuse, under all the disadvantages with which the
power there acts, and after having known that the power of steam is equal to
that of the fuse, could any longer doubt of the sufficiency of the power of
steam to do any thing, even to carry the whole engine up into the air. If so,
why will it not do to propel carriages and boats? For twenty-one years last
past I have been endeavouring to convince my countrymen, that principles do
exist by which steam engines can be made useful in all cases where a powerful
agent is wanted. I sent, early in 1795, drawings and specifications to England
and had them shown to engineers there, all without effect. I am sorry to
relate, that seventeen years passed before I could conceive it to be my
interest to expend one thousand dollars, to try experiments to put my
principles in practice. In 1801, I commenced, and at the expense of two
thousand dollars, besides my own labour and time, valued at one thousand
dollars more, I at last produced an engine realizing in practice the whole of
my theory. Having now made perhaps the greatest improvement, and most useful
invention on steam engines ever produced by any one man, I expect to be
attacked from all quarters: in every state in the union will, no doubt, be
found one or more inventors who have made the same invention, as was the case
with my improvements on merchant flour-mills, after they were published. In
that case I was attacked from a quarter from which I could not possibly expect
it; but the justice of my country continues to give me the honour (I wish I
could say, and the profit) of my invention.
Experience now teaches, that if 4 pecks of fuel
per hour, will heat a quantity of water to produce steam of elastic power equal
to 15 pounds to the inch, or equal to one atmosphere, 5 pecks consumed per
hour, will produce steam equal to 30 pounds the inch, or two atmospheres, and
keep the power up to work an engine; * holding true in practice, that every
addition of a small quantity of fuel to be consumed in an equal time, doubles
the elastic power of the steam, and keeps it up to work an engine; double fuel producing
about 16 times the bulk, consequently 16 times the power and effect. This will
not appear doubtful, after we are informed, that philosophers have made a set
of accurate experiments, to ascertain the elastic power of steam produced by
different degrees of heat, from which they deduced the following formula or
rule, viz. That every addition of about 30 degrees of heat, by Fahrenheit's
thermometer, to the water, be the temperature what it may, doubles the bulk and
elastic power of the steam.
*1089
pounds of dry oak are equal to 600 pounds of Newcastle coals, in producing
equal quantities of heat. Repertory of Arts, series ii. vol.1.
See the experiments in the American edition of
the Encyclopedia, vol.17, from which the following scale is constructed.
SCALE OF THE ELASTIC
POWER OF STEAM, PRODUCED
|
|
Degrees
of heat in the wateradding 30 degrees every step |
Elastic
power to the inchare of piston, or safety valve. |
Atmopsheres |
|
|
212
gives |
15
pounds, equal to |
1 |
|
|
242 |
30 |
2 |
|
|
272 |
60 |
4 |
|
|
302 |
120 |
8 |
|
|
332 |
240 |
16 |
|
|
362 |
480 |
32 |
|
|
392 |
960 |
64 |
|
|
422 |
1920 |
128 |
By this scale it appears that doubling the heat
from 212 to 424 degrees in the water, produces 128 times the elastic power of
steam; and that as the heat is increased in an arithmetical progression, by the
addition of 80 degrees, the elastic power of the steam is increased in a
geometrical ratio, multiplying by 2. But this may be only true at or near the
heat of 212 degrees; the geometrical multiple being greater than 2 below 212
degrees, and less than 2 above 212 degrees of heat; falling short 15/1000
parts, at every step of 11 1/4 degrees increase of heat, as has been the result
of another set of experiments, made by Dalton.* So that doubling the heat in
the water, may not produce more than 75 or 100 times the elastic power of
steam.
*See
the Repertory of Arts, vol i. series 2.
Let us suppose it to be true, as was heretofore
believed, that double power of steam requires double fuel to produce it; then
by the scale, if 212 degrees of heat give power equal to 15 pounds, and require
1 bushel of fuel, 242 degrees giving 30 pounds power, will require 2 bushels,
and so on to the end of the scale. 424 degrees of heat, double 212, would
require 128 times the fuel to produce it, which is quite absurd. It is much
easier to conceive, that double heat would produce 128 times the power.
Although double fuel will not produce near double heat, yet it is easy to
conceive, that it may give such heat, as will produce 16 times the power. We
should observe also how rapidly the proportionate quantity of heat diminishes,
which is required to be added, in order to gain power, as the water rises in
temperature.*
*See
the American edition of the Encyclopedia, vol 17.
Although experiments have been made with great
care and accuracy, to ascertain the fact as to the rapidity of the increase of
the power of steam, compared to the increase of heat in the water, yet I find
no attempts made to apply the principle, nor even a suggestion to that effect,
in any of the books that have ever fallen into my hands. But the result drawn
by Dalton cannot be true, because his scale continued, the increase of the
elasticity by the increase of heat, would entirely cease before the power could
be augmented sufficiently to produce the effects which have been produced.
SCALE OF EXPERIMENTS.
|
Temperature of the
water |
Elastic power of steam |
Proportional heat to
be added to the temperature which the water may be in, to double the power |
|
Degrees |
lbs. |
|
|
10 |
.11 |
3 |
|
40 |
.23 |
.75 |
|
70 |
.46 |
.42 |
|
100 |
.93 |
.30 |
|
130 |
1.87 |
.23 |
|
160 |
3.75 |
.19 |
|
190 |
7.5 |
.16 |
|
220 |
15 |
.14 |
|
250 |
30 |
.12 |
|
280 |
60 |
.11 |
|
310 |
120 |
.09 |
|
340 |
240 |
.085 |
|
370 |
480 |
.08 |
|
400 |
960 |
|
By this scale of experiments, it appears, that
when the water was in the temperature of 10 degrees, the elastic power of the
steam was but 11/100 parts of 1 pound to the inch, and the heat required to be tripled,
by adding 30 degrees to double the power. But when the heat was raised to 220
degrees, the power was 15 pounds, and required but 14/100 parts of the heat to
be added, or 30 degrees to double the power to 30 pounds. Here 30 degrees
increase of heat gained 15 pounds, whereas in the low temprature of 10 degrees,
the 30 degrees added, gained but 12/100 parts of 1 pound. When the water is
heated to 370 degrees, and the power of steam raised to 480 pounds to the inch,
it requires but 30 degrees additional heat, or 8/100 parts of the heat of the
water, to be added to gain 480 pounds more power. If the reader has faith to
believe thus far, he is ready to ask, by what unaccountable law of nature is
the elastic power of steam produced in this ratio, so variable as to the
quantum of additional heat, required to gain a given quantity of power? for hy
the last addition of 30 degrees of heat in this scale, we gain 4363 times as
much power as by the first addition.
I answer, it is enough for us to know by
experience that it is so, to enable us to avail ourselves of the application of
the principles. It clearly points out to us the great gain tobe had by working
with high temperatures; for if doubling the consumption of fuel produces six.
teen times the bulk and power of steam, it enables us to produce eight times
the effect, with equal quantities of fuel, and I am inclined to believe, that
the application of the principles may be improved to that extent. But we should
not rest satisfied, until we are able to assign philosophical reasons why it is
so, which leads us to treat of heat.
OF HEAT.
HEAT, I conceive to be an elementary principle,
existing as a component part of all substances, but in different proportions.
Combustibles contain the largest quantities, in that state which Dr. Black, the
celebrated Lecturer on Chemistry, has called a latent, or state of secret
inactivity.
Combustion is the operation by which this latent
principle is excited into action; all that is contained in the body or matter
consumed, as well as all contained in the air used in the operation, is changed
into a state of activity, susceptible of being transmitted from one body to
another, until it finds rest or becomes latent again. The principles are too
mysterious for our comprehension, we can only observe the effects. We can see
that heat in the operation of combustion, appears to melt the fuel, or dissolve
it into a fluid, so thin and rare as to be imperceptible. It is dissipated and
flies away into the air, where the heat becomes latent again. The expansive
force of fluids formed by heat, is the subject under consideration; the
atmosphere is the great reservoir into which all active heat returns to a
latent state.* Let us suppose each column of the atmosphere, whose base is equal
to a square foot, contains an equal quantity of latent heat, of water in a
state of vapour, and of the permanent elastic fluids; and suppose one of those
columns of air to be included in a cylinder, and
compressed into half the space; then, by the Boylean law, (see article 6) it
would have double elastic power, if compressed into one tenth part of the
space, ten times the elastic power, if into one hundredth part of the space,
one hundred times the power, &c. The aqueous vapour would be pressed into hot
water, in the bottom; the latent heat would become active, heat the cylinder,
escape into the surrounding air, and then become latent again. Then if the
piston were suddenly drawn up, the alr could not expand to its original bulk,
having lost its proportion of latent beat and water, until that proportion
would be restored. That the results would be as stated has been proven.** These
serve to shew that compressed air or strong elastic steam do not contain as
much heat in a latent state as weaker, in proportion to their power, and that
the Boylean law is an error.
*It
may pervade all space, which ancient philosophers held was filled with what
they called ether.
**See
the American edition of the Encyclopedia.
Experiments were made to ascertain the
elasticity of air, in proportion to its density, by condensing it in a cylinder
with a piston. It was found that double density did not produce quite double
elasticity, nor quadruple density quadruple elasticity, &c. The
experimenters were surprised to find, that great compression made the cylinder
hot, and filled a vial, which they had inserted in the bottom of the cylinder,
with water. From this experiment we may safely infer, that air and steam do not
contain heat in direct proportion to their density, but rather in an inverse
ratio, that is, the greater their density the less latent heat they contain in
the space they occupy; that a vacuum contains more latent heat than a plenum,
and that the atmospheric air is not a permanent elastic fluid.
If heat be applied to melt ice of the
temperature of 32 degrees of Fahrenheit, 147 degrees of it find rest in the
water made by melting the ice, and is necessary as a constituent part of the
water to keep it in a fluid state, latent and imperceptible to the thermometer,
which indicates it to be of the same temperature the ice was in. If we continue
to apply heat to the water until we raise its temperature to 212 degrees, it
will begin to produce elastic vapour, equal in power to the weight of the
atmosphere, which it now lifts and continues to resist. In this vapour under
the pressure of the atmosphere, from 800 to 1000 degrees of heat, returned into
a latent state, find rest; being, under that pressure, a constituent part of
vapour, and necessary to continue it in that state; the thermometer indicating
the same degree of heat as of the boiling water, which is 212 degrees. This is
proven by Dr. Black.*
*See
his Lectures, vol.1.
If the weight of the atmosphere be taken off the
water, it will boil at 70 degrees of heat; but in this case, 1300 or perhaps
2000 degrees of heat in this weak vapour, find rest or become latent rising
under no pressure. The less the pressure on the surface of boiling water, the
more heat is required to raise it all into vapour; on the contrary, the greater
the pressure, or the greater the elastic power of steam, the less the heat or
fuel required to raise it all into vapour. The heat cannot find room, amongst
the particles of strongly compressed steam, to become latent, but remains
active to increase the power. If we increase the pressure on the surface of the
water from 1 to 8 atmospheres, it will not boil until the heat be increased 90
degrees above 212; that is, 302 degrees, when the power of the steam will be
120 pounds to the inch. (See the scale, art. 3). The water will then begin to
boil, and the steam to rise, lifting the weight of 8 atmospheres an equal
distance in equal time, which may be compared to a load on an engine. Here it
appears that, after the loss of heat occasioned by its becoming latent ceases
(as all that loss takes place in raising the temperature the first 212
degrees), we can, by the addition of the small quantity of fuel which will be
required to increase the heat 90 degrees, gain 8 times the power, produce 8
times the effect, or carry 8 times the load an equal distance. But we will
show, in the proper place, that steam of power equal to 8 atmospheres can be
applied to work an engine, to produce much more than 8 times the effect. See
art. 7, where it is shewn that it produces 22.6 the effect, or perhaps 32
times.
As heat appears to melt or dissolve the fuel in
combustion, into a thin elastic fluid, with which it passes off into the air to
return to a latent state; so it appears to dissolve the water into a much
thinner fluid called elastic steam, with which it passes off into the air,
there to find rest in a latent state. The quantity of beat passing off, appears
to be in some ratio to the space into which the steam is permitted to expand
and occupy; perhaps in direct proportion, that is, double space may be capable
of receiving double quantity of heat in a latent state. One cubic inch of water
rising freely into steam in vacuo, carried with it 1300 or perhaps 2000 degrees
of heat in a latent state, while the same quantity rising under the pressure of
the atmosphere, which confines the steam to a less space, carried off but 1000
degrees of heat in a latent state; from which we may safely infer, that as the
pressure is increased from 1 to 2, and so on to 8 atmospheres, or the steam
confined to a smaller space, by giving it a greater load, that the heat carried
off in a latent state will be lessened from 1000 to 750, 500, 250, 125 degrees,
or in some other ratio not yet ascertained.
As heat enters water, formed by melting ice,
slowly, and becomes latent in the water, so it also leaves the water slowly,
becoming sensible or active again as the water freezes. But on the contrary, as
the heat leaves hot water quick as lightning (comparatively speaking) when the
compression is taken from off its surface, be coming latent in the form of
elastic vapour, so also it leaves the vapour instantly, to enter water or other
matter of a lower temperature, and the vapour is condensed, forming the same quantity
of water which was used in its formation; the heat becoming active and sensible
to the thermometer, which will indicate the rise of temperature in the water
used to condense it: all which has been proven by Doctor Black, although not
shown in the very same point of view.* When we consider the irresistible power
of steam, we may say, with propriety that we have at our command a physical
agent, whose operations are quick as lightning, and powerful as thunder.
*See
his Lectures, vol 1.
From the foregoing facts we may safely draw the
following inference, viz. That the quantity of water necessary to condense any
quantity of elastic steam, under any pressure, will be such as is just
sufficient to receive all heat from the steam, into the water, leaving it of the
temperature at which water is just ready to boil under such pressure; therefore
the colder the water, the less will be required. If the condensation be made
under no pressure, or in a vacuum, it will require a much larger quantity of
cold water, because it will not bear to be heated to 70 degrees, the boiling
heat of water in vacuo.*
*A
competent knowledge of those principles, leads us directly to the discovery of
a variety of curious and important improvements and inventions, which may lead
on to others, viz.
1. Steam engines which will be inexhaustible in
their operation. Once filled with water they will require no supply; no
sediment can accumulate to cause the boilers to burn out; they will therefore
last much longer.
2. Stills to suppress the watery vapour and
essential oils which give the spirits a bad flavour, and to take off the
spirits pure at one operation, which may be made perpetual, or without
intermission.
3. Boilers for distillers and brewers, by which
their largest vessels can be heated to any degree, in a much shorter time, and
with less expense.
4. Inexhaustible boilers for heating apartments
where fire would be dangerous, if used in the common way.
5. Furnaces and boilers may be so constructed,
that all the heat, which in common furnaces ascends the flue or chimney, may be
poured immediately into the water, to generate steam; and all the elastic fluid
generated by the consumption of the fuel, applied to aid the steam in working
the engine; lessening the weight of the engine to about one-tenth part, and the
consumption of fuel to about one-fourth part, and yet produce as much power as
the best English engines. An engine thus constructed will be the most suitable
for the great purposes of propelling boats against the stream of the Mississippi,
and carriages on turn-pike roads, &c.
Here it appears almost impossible to form a
perfect vacuum, by condensing the steam with water, by the use of condensers to
steam engines; all their use being to take off the resistance of the
atmosphere, which can be effected in part only, and considering the very small
quantity of additional fuel required to overcome that resistance, their
advantages seem to vanish. For if the condensing water be heated to 160
degrees, then, by the scale of experiments, (art. 3.) the power of steam left
in the condenser will be 3.75 pounds to the inch; this deducted from 15 leaves
11.25 pounds, which is all the resistance taken off by the condenser. Again, if
we supply our boiler with this condensing water of the temperature of 160 degrees,
it will lower the temperature in the boiler perhaps 30 degrees, from 310 to 280
degrees, and by that means reduce the elastic power of the steam from 120 to 60
pounds, (see the scale, article 3.) which would be losing 22.4 pounds, the
average of 60 pounds, to gain 11.25.* (See the scale article 6.)
*But
if this supply-water be driven first into a vessel, through which the flue of
the furnace is made to pass, to heat it to the temperature of the water of the
boiler before it enters, it will not then reduce either the heat or power of
the steam.
But the expense of the experiments necessary to
bring these principles into operation would be too great. No prudent man will
risk the attempt, until the prospects of a sufficient reward brighten. We unite
in a belief, that fate has ordained that the ingenious man shall never be rich;
not considering that it is the injustice and impolicy of most governments, that
have passed the decree. Who would get rich if the property he acquired by his
industry was to become common as soon as he gained it? or even if it was to be
the case at the end of fourteen years. What prudent man will spend his
thoughts, time, labour and money, for property no better secured to him.
Ingenuity makes none poor, but on the contrary, has made many rich, whose
prudence directed them to the pursuit of permanent property. To ingenuity we
owe all our superiority over savage nations. England has made herself more rich
and powerful than other nations, by her more liberal policy of securing to ingenious
men, the exclusive right to their inventions, so long as to afford them an
opportunity of being amply rewarded.
RECAPITULATION.
I have shown,
1st, That a great quantity of heat is expended
in raising the temperature of water to a boiling degree, or 212 degrees, to
produce steam of elastic power only equal to the pressure of the atmosphere,
which is equal to 15 pounds to the inch surface of the water.
2dly, That the elastic power of the steam
increases in a geometrical ratio, as the heat increases in an arithmetical
ratio; every addition of about 30 degrees or heat in the water, doubling the
elastic power of the steam; so that doubling the heat of the water increases
the power of the steam about one hundred times.
3dly, That the proportional quantity of heat to
be added to double the power, decreases in a rapid ratio as the heat in the
water increases; that by adding 30 degrees of heat to the high temperature of
370 degrees, we gain 4363 times as much power as we gain by adding 30 degrees
to the low temperature of 10 degrees.
4thly, That the heat escapes in a latent state
in weak steam, in much greater quantity in proportion to the power, than it
does in strong elastic steam; that this loss of heat in a latent state may be
in direct proportion to the space in which the steam is suffered to expand.
This has been proven by John Dalton.*
*See
his experiments...Repertory of Arts, vol. ii. series 2.
1st, He placed a thermometer in the centre of a
large receiver, and condensing the air by forcing more in, the thermometer rose
quickly several degrees, and opening the cock to let the air escape, it sunk
quickly several degrees lower than the temperature of the atmosphere. Why were
these effects produced? I answer, because when the air was condensed, there was
not room for the heat to remaln in the receiver in a latent state; and in its
efforts to find room, it became active, ran into the thermometer, expanded the
quicksilver; and caused it to rise: but if left in that state, the heat soon
passed through the glass receiver, and an equilibrium being restored, the
thermometer settled to its proper degree. When the cock was opened, the air
escaping, left more room for latent heat than could be filled by the heat left
in the receiver, therefore the heat in the thermometer left it, and the mercury
contracted and fell to meet the temperature of the space inside of the
receiver, but being left in that state, the equilibrium was soon restored, by
the heat of the surrounding atmosphere entering through the glass receiver.
2dly, Exhausting the receiver, the thermometer
fell suddenly several degrees, because this increased the capacity of the space
within the receiver for receiving and retaining heat in a latent state, which
deprived the thermometer of its heat. But an equilibrium was soon restored, by
a supply from the surrounding atmosphere.
These experiments clearly prove that a vacuum
has a greater capacity for heat in a latent state than a plenum; and no other
inference can be rationally drawn from the premises. They also clearly account
for the wonderful effects produced by my new principle of confining the steam,
and increasing the heat in the water, by which the elastic power of the steam,
is increased; so that doubling the fuel, produces about 16 times the effect;
enabling us, with small, simple, and cheap engines, to obtain power equal to
the larger, more complex, and expensive ones, heretofore used, and with
one-third part of the fuel. Although we cannot account philosophically for all
these operations of nature, yet we may be satisfied with a knowledge of the
facts.
It appears therefore, that to begin to use steam
when it has arrived to only atmospheric power, is to stop at the point where
the heat begins to produce power without loss, after which every degree of heat
we add, serves with effect to increase the power in a rapid ratio. The less we
confine the steam, the more fuel will be necessary; and the more we confine the
steam, or the heavier we load the engine, the less fuel will be required to
produce the effect we wish. Every stroke of the engine will draw off nearly an
equal quantity of heat, let the load be light or heavy, and we may at least
safely conclude, that the increase of fuel or heat used, will bear no
proportion to the increase of load. (See art. 3,)
OF THE CONSTRUCTION
OF BOILERS.
As we mean to work with steam of great elastic
power, say 120 pounds to the inch, above the atmosphere, it is necessary, in
the first place, to discover true principles, on which we may calculate the
power exerted to burst our boilers, by any given power cf the steam; that we
know how to construct them with a proportionate strength, to enable us to work
with perfect safety.
A circular form is the strongest possible, and
the less the diameter of the circle, the greater elastic power it will contain.
Therefore we make cylindrical boilers not exceeding 3 feet diameter, and to
increase their capacity we extend their length to 20 or 30 feet, or more, or
increase their number. They must be set nearly in a horizontal position, with
the furnace under one end confining the flue to the underside to the other end;
giving the fire a large surface to act on. This is the most simple form and
suits well where fuel is cheap. But to save fuel we construct boilers
consisting of two cylinders, one ]nside of the other; the inner a little below
the centre of the outer one, when laid in a horizontal position, to give room
for steam, in the upper side above the surface of the water. They are of equal
length, both made list to the same heads or end-plates. The space between them
contains the water, and the inner one contains the fire, which is surrounded by
the water. This boiler is enclosed in brick work, and the flue returned along
the under side of the outer cylinder which gives the fire a larger surface to
act on, than the other plan, and will not require more than two-thirds of the
fuel; but it is much more expensive to make.
These boilers are made of the best iron, rolled
in large sheets and strongly riveted together. The ends may be made of soft
cast iron, provided the fire or flue be kept from immediate contact with them.
As cast iron is liable to crack with the heat, it is not to be trusted
immediately in contact with the fire.*
*It
has been said that using a great degree of heat will burn the stuffing of the
piston of the engine. But I have boiled linseed oil in a wooden boiler, with a
furnace inside of it, without burning the wood, which will not bear a greater
degree of heat then the hempen stuffing, and by the scale of heat(art.11)
linseed oil boils at 600 degrees of heat. If the scale(art.3) be continued or
extended to that degree of heat in the water, the elastic power of steam would
be 122,880 pounds to the inch, which shows the futility of such objections,
even supposing the scale to be incorrect, and that linseed oil will boil at a
much lower degree.
To ascertain the power exerted by the steam, to
burst one of these boilers, and the thickness of iron necessary to hold it; let
us premise, that it is known by experiments made with care, (see art. 11) that
a bar of good, sound, wrought iron, 1 inch square, will bear from 68 to 84,000
pounds, (but let us say from 64 to 75,000 pounds) hung to the end of it, to
pull endwise, in a fair straight direction; consequently a bar one-tenth of an
inch thick, and one inch wide, will hear at least 6400 pounds.
RULE.
Multiply the diameter of the boiler in inches,
by the power of the steam in the boiler, in pounds, shown by the weight on the
inch area of the safety valve, and the product is the power the steam exerts to
break each ring of one inch wide, in any two opposite places. Take half of that
product for the power to break it in any one place, and divide by 6400, and the
quotient will be the thickness in decimal parts of an inch, that the iron must
be to hold that power.
EXAMPLE.
What is the power exerted to burst a boiler 36
inches diameter, when the steam is ready to lift the safety valve loaded with
1500 pounds to the inch? and what thickness must the iron be to hold that
power?
Then by the rule, 36 multiplied by 1500, the
product is 54,000 pounds, the power to break every ring of 1 inch wide in any
two opposite sides: and 54,000 divided by 2 quotes 27,000 pounds, the power
exerted to break each ring of 1 inch wide in any one place; and 27,000 divided
by 6400 quotes 42/100 parts of an inch, the thickness of the sheet iron that
will hold that great power, of 1500 pounds to the inch. Few will believe this
until they clearly understand the pnnciples. I proceed therefore to demonstrate
the rule to be true.
DEMONSTRATION.
Suppose the circle, 36 inches diameter, be
inscribed in a square, whose sides are 36 inches in length; draw diameters to
the circle, parallel to the sides of the square; and, suppose steam to exert a
power in the square, equal to 1500 pounds to each inch; it is evident that
there will be 1500 pounds on every inch of the length of any two opposite
sides, exerted in opposite directions balancing each other, to separate the
sides, which are held together by the other two sides; add that to find the
power exerted to break any two opposite sides, we must multiply the length of
one of the sides, 36 inches, by 1500, the power of the steam, and the product
is 54,000 pounds, to break the two sides; half of which is 27,000, to break one
side in any one place.
Again, suppose the circle to intercept the steam
from acting on the square, then it is evident that each semicircle intercepts
the steam which acted against its corresponding side of the square, and that
the power to break the circle in any two opposite places is just equal to the
power to break the two sides of the square; which was to be demonstrated.
This may be demonstrated by the proportions of
the circle, and the known laws of mechanical powers. Let us suppose the
circumference of the circle, which is 113 143/1000 inches in length, to be a
cord with one end made fast, and a power be applied to draw the other end of it
in a straight line, so as to draw the whole l13 143/1000 powers of the steam, 1500
pounds each, amounting to 169,714 5/10, up to the centre; then these powers
multiplied into their distance moved, which is 18 inches, will produce
3,054,865; and the power at the end of the cord, 27,000, multiplied into its
distance moved, viz. the whole length of the circle, 1l3 143/1000 inches,
produces the same sum, 3,054,865, agreeing with the known law of mechanics,
viz. that the power multiplied into its distance moved, is equal to the weight
multiplied into its distance moved. The power at the end of the cord, 27,000
pounds, representing the strength of the hoop necessary to hold a power of 1500
pounds to the inch, exerted inside of it: which was to he demonstrated.
I have never found a solution of this so useful
problem that so often occurs in practice, in arranging steam engines,
water-works, pipes of conduit, &c. And, no doubt, but the simple rule, here
laid down, will meet with opposition; but it is nevertheless true, and will
stand the test of time and experiment. I rejoice at having discovered, that a
circular vessel will hold a far greater power of steam than I at first
conceived it would.
In order that we may work with a power of steam
equal to 120 pounds to the inch, with peffect safety, I have, by the rule
already demonstrated to he founded on true principles, calculated the following
table, shewing the power exerted to burst each ring of 1 inch wide of the
boilers of different diameters, and the thickness of iron necessary to hold
steam of power equal to 1500 pounds to the inch area.
A TABLE OF THE DIAMETERS
AND STRENGTH OF BOILERS.
|
Diameter of the boiler ortube in inches |
Power to break everyring of one inch ofthe boiler in anyplace, in pounds weight,when the steam is1500 pounds to the inchon the safety valve. |
Thickness of thesheets of goodiron necessary tohold the power,in decimal partsof an inch |
Power exertedon the headsto burst themout, in poundsweight |
|
42 |
31,000 |
.48 |
2,077,500 |
|
40 |
30,000 |
.46 |
1,884,000 |
|
36 |
27,000 |
.42 |
1,525,500 |
|
30 |
22,500 |
.35 |
1,069,000 |
|
25 |
18,750 |
.29 |
735,000 |
|
20 |
15,000 |
.23 |
471,000 |
|
15 |
11,250 |
.17 |
|
|
12 |
9,000 |
.14 |
|
|
10 |
7,500 |
.12 |
|
|
8 |
6,400 |
.094 |
|
|
7 |
5,250 |
.082 |
|
|
6 |
4,500 |
.07 |
|
|
5 |
3,750 |
.058 |
|
|
4 |
3,200 |
.047 |
|
|
3 |
2,250 |
.035 |
|
|
2 |
1,500 |
.023 |
|
|
1 |
750 |
.012 |
|
|
Diameter ofthe boiler ortube in inches |
Strength of boilerto hold the head on,in punds weight |
Number of inchscrew boltsnecessary to have strengthsufficient to hold on the heads |
Thickness of the cast iron head in the middle in inches |
|||
|
42 |
4,052,400 |
32 |
5 |
|||
|
40 |
|
29 |
4,5 |
|||
|
36 |
2,037,440 |
24 |
4 |
|||
|
30 |
|
16 |
3.5 |
|||
|
25 |
|
11 |
3 |
|
|
|
20 |
918,777 |
8 |
2.5 |
|||
A boiler constructed from this table will hold
steam with power equal to 1500 pounds to the inch; a power almost beyond
conception, and which we will never need to work any engine. To find the number
of inch screw bolts necessary to hold on the head, divide the force to burst
the head off; by 64,000, the strength of one bolt.
***** to the end, where it should just balance
the atmosphere when another valve opens to let in a similar puff of steam to
drive the piston up again; while other valves open to let the steam escape from
before the piston. Thus the piston is driven by strong puffs of steam, the same
as an air-gun drives its bullets; with this difference, the air-gun is soon
exhausted, but the fire keeps up the power of the steam; the whole power of the
steam is expended on the piston, before it leaves the cylinder, except what is
necessary to resist the atmosphere. This is supposing the engine to work
without a condenser.
OF THE MEANS OF
APPLYING STEAM.
Supposing that no doubt can now remain in the
mind of the intelligent reader, of our being able to work with steam of power
equal to 120 pounds to the inch, with great advantage and safety, we will
proceed to consider of the most economical means of using or applying this
power, so that it may produce the greatest effects.
The engine may be constructed similar to that of
Bolton and Watts, except the gears for working the valves, which should be so
arranged as to open the valve, when the piston is up, to let in a puff of the
strong steam to drive it down, but to shut again as soon as enough has got in,
which, when suffered to expand, will fill the cylinder with atmospheric power
only; the steam entering the cylinder with a power of 120 pounds to the inch,
drives the piston with great force; but the valve being shut at 1/8 part of the
stroke, the steam expands and decreases in power, all the rest of the stroke,
A TABLE
Showing the proper time
to shut off the steam, according to the power in the boiler; and how the power
and load it will carry at every part of the stroke diminishes, in order that
the steam may spend all its power; supposing the lengths of the stroke divided
into eight equal parts, and working without a condenser.
|
|
Power of steam in the boiler, 120 pounds to the inch |
Load, deducting 15 pounds for the resistance of the atmosphere. |
Power of steam in the boiler 60 pounds to the inch. |
Load, deducting 15 pounds for the resistance of the atmosphere. |
Power of steam in the boiler 30 pounds to the inch. |
Load, deducting 15 pounds for the resistance of the atmosphere |
Power of steam in the boiler 15 pounds to the inch. |
Load |
|
1 |
120 |
105 |
60 |
45 |
30 |
15 |
15 |
0 |
|
2 |
60 |
45 |
60 |
45 |
30 |
15 |
15 |
0 |
|
3 |
45 |
30 |
45 |
30 |
30 |
15 |
15 |
0 |
|
4 |
30 |
15 |
30 |
15 |
30 |
15 |
15 |
0 |
|
5 |
26.25 |
11.25 |
26.25 |
11.25 |
26.25 |
11.25 |
15 |
0 |
|
6 |
22.5 |
7.5 |
22.5 |
7.5 |
22.5 |
7.5 |
15 |
0 |
|
7 |
18.25 |
3.25 |
18.25 |
3.25 |
18.25 |
3.25 |
15 |
0 |
|
8 |
15 |
0 |
15 |
0 |
15 |
0 |
15 |
0 |
|
|
|
52.5 |
|
22.5 |
|
7.5 |
|
0 |
|
|
|
269.5/8 |
|
179.5/8 |
|
89.5/8 |
|
0 |
|
|
|
33.7 |
|
22.4 |
|
11.2 |
|
0* |
|
|
|
15 |
|
15 |
|
15 |
|
15 |
|
|
|
48.7 |
|
37.4 |
|
26.2 |
|
15** |
*Average
load without a condenser.
**Average
load with a condenser.
The foregoing table is founded on the supposition
that the elastic power of steam is governed by the same laws, which govern the
elastic power of permanent elastic fluids, viz. That their elasticity is in the
inverse pro-portion with the space they occupy; or, as their density, called
the Boylean law, (article 4.) If compressed into half the space their power is
doubled, and if expanded into double space, their power is reduced to one half.
But this is not strictly true with steam, because it is not a permanent elastic
fluid. There will not as much heat enter into 1/8 part of the cylinder, with
steam of 120 pounds to the inch elastic power, as will he sufficient to cause
it to expand to fill the whole cylinder with elastic power, equal to 15 pounds
to the inch, to resist the atmosphere (see article 4); it will not bear,
therefore, to he shut off so soon. If a sufficient quantity of steam be
admitted, to contain heat to expand it to fill the cylinder with power equal to
the resistance of the atmosphere, the average load of the stroke will be greater
than is shown by the table.
When the steam is 120 pounds to the inch, as in
No.1 of the table, by the law it requires to be shut off at 1/8 part of the
stroke, to give the steam time and room to spend all its power in driving the
piston to the end, and to fill the cylinder with steam, equal to 15 pounds to
the inch, just sufficient to resist the atmosphere the effective load being
always 15 pounds less than the power of the steam, diminishes from 105 pounds
to the inch, the load when the valve shuts, to 0 at the end of the stroke.
To find the average load or the load the steam
will carry the whole stroke, and resist the atmosphere, add the different loads at each division
together, and to that sum (for the deficiency that is occasioned by not
dividing the stroke into an infinite number of divisions) add half the load at
the time the valve was shut, that is half of 105 pounds, equal to 52 5/10
pounds, and it makes 269.5 for the effect of the stroke; which divided by 8,
the number of divisions, and it quotes 33.7 pounds, the average load; to which
add 15 pounds and it makes 48.7 pounds the average load, when a condenser is
used to take off the resistance of the atmosphere.
When the steam is 60 pounds to the inch power,
as in No.2, in the table, it requires to be shut off at 2/8 of the stroke, and
the average load against the atmosphere is 22.4 pounds to the inch, and with a
condenser, 37.4 pounds.
When 30 pounds to the inch power, as No. 3, it
requires to be shut off at 4/8 of the stroke, the average load against the
atmosphere being 11.2 pounds to the inch and with a condenser 26.2 pounds. And
when the steam is 15 pounds to the inch power, as No. 4, it requires to be shut
off at the end of the stroke, the average load against the atmosphere being 0,
and with a condenser of 15 pounds to the inch.
Now it is evident that, as the cylinder is to be
filled with steam in each case, just equal in power to the resistance of the
atmosphere, or equal to 15 pounds to the inch, therefore it contains an equal quantity
of heat in each case; although die effects are so different, that when we work
without a condenser, the strong elastic steam, 120 pounds to the inch, carries
a load of 33.7 pounds to the inch; while steam of 60 pounds power, carries but
22.4 pounds; steam of 30 pounds carries 11.2 pounds, and steam of 15 pounds
carries 0, above the resistance of the atmosphere, and with a condenser to take
off that resistance, the loads are 48.7, 37.4, 26.2 and 15 pounds to the inch,
by the law of permanent elastic fluids on which the table is founded. But as it
has been shown (article 4) that strong elastic steam does not contain heat in
proportion to its power compared with steam less elastic; it is probable that
in No. 1 the valve must be kept open ~ of the stroke, which would increase the
average load to about 80 pounds to the inch; so that it appears that on this
new principle, by confining the steam until its elastic power rises to 120
pounds to the inch, we can produce about 6 times the effect from equal quantities
of heat, that can be produced, if we use it with power equal to 15 pounds. And
if this be done with equal quantities of heat drawn from the boiler, we may
conclude that nearly equal quantities of fuel will be used in each case,
because the compression of the strong elastic steam on the surface of the water
in the boiler, creates no obstacle to the heat passing from the fire into the
water, but rather facilitates it; because solid bodies receive heat more freely
than porous ones.
Suppose the cylinder requires to be filled 1/3
part with steam of 120 pounds to the inch, to admit heat sufficient to expand
the steam to fill the cylinder with a power equal to 15 pounds to the inch, and
divide the cylinder into 9 parts, then by the principles laid down, the load at
the end of the several divisions, will be nearly as follows, when we use a
condenser.
|
1 |
120 |
|
2 |
120 |
|
3 |
120 |
|
4 |
100 |
|
5 |
80 |
|
6 |
40 |
|
7 |
34 |
|
8 |
27 |
|
9 |
15 |
|
10 |
60 Half the power when shut off |
|
11 |
716/9 |
79.55 pounds, the average load being more than
six times the load of the old principle, which is not above 12 pounds. This is
effected by drawing from the boiler an equal quantity of heat at each stroke,
in each case. This however is a mere inference drawn from the premises
supposing that a vacuum has a greater capacity for receiving heat than a
plenum, (see art. 4.)
35
COMPARISON
OF THE PRINCIPLES.
To compare the two
principles, viz. That of working with atmospheric steam to form a vacuum, which
owing to its imperfection, seldom carries a load exceeding 12 pounds to the
inch, with the new principle of working with strong elastic steam, equal to 120
pounds to the inch, which, shut off at 1/8 part of the stroke, (as No.1 in the
table, article 6) carries a load equal to 48.7 pounds to the inch.
By article 3,
every addition of a small quantity of fuel doubles the power and bulk of the steam;
so that there remains no doubt but that doubling the fuel, that will produce
atmospheric steam, will increase its elastic power to 120 pounds to the inch
and move 8 times the the load an equal distance; producing 8 times the effect
on that simple principle. But when we consider that we shut off at 1/8 part of
the stroke, and are enabled to strike 8 times the number of strokes, carrying a
load of 48.7 pounds, which, multiplied by 8 is equal to 389.6, the effect.
Hence it appears that by doubling the fuel to obtain the strong steam, 32 times
the effect is produced by the new principle.
But we rather
believe that the steam will not bear to be shut off sooner than at 1/4 the
stroke, which increases the average load to about 68 pounds to the inch, and
enables us to strike only 4 times the number of strokes; then 4 multiplied by
68 is equal to 272, which, divided by 12, the load of the old principle, quotes
22.6 times the effect.
Again, let us
suppose a boiler with a furnace to consume 1 bushel of coals in an hour, with a
cock opened so wide as just to let the steam (when its power is 15 pounds to
the inch) escape freely into a vacuum. It has been ascertained that the
velocity would be 1332 feet per second. Then suppose we increase the
consumption to 2 bushels per hour, leaving the aperture the same; we believe
the elastic power would be increased to 120 pounds to the inch, and the
velocity of the steam would be as the square root of the pressure, viz. 3769
feet per second, we may say as quick as lightning, and the effects will be as
the pressures multiplied into their velocities by the known laws of mechanics.
Then, 15 multiplied by 1332 is equal to 19,980, the measure of the effect
produced by 1 bushel of coals per hour, and 120 multiplied by 3769 is equal to
452,280 the measure of the effect produced by 2 bushels of coals per hour,
452,280 divided by 19,980 quotes 22.6, that is 22.6 times the effect produced
by doubling the fuel.
We
have not made experiments sufficiently accurate nor discovered data from which
we can calculate the different effects with accuracy, but we know enough by
experience with an engine in actual use, working on the new principle in the
most simple form, without a condenser, to be assured that the gain of power and
saving of fuel is very great; and may say with safety, that doubling the fuel
on this principle, produces at least 16 times the power and effect.
OF THE SUPPLY PUMP.
WE supply the boiler with water by a small
forcing pump, wrought by the engine, which requires about one thousandth part
of the power to work it, to force a little water into the boiler at every
stroke, and we experience great loss of power by using cold water as a supply;
for although it lowers the heat in the boiler but little, yet as it has been shown,
that a small increase of heat, say 30 degrees, doubles the power, so a small
diminution of heat, say 30 degrees, reduces the power to one half; say from 120
pounds to 60 pounds to the inch, (see article 3.)
Therefore we construct a strong, small vessel
called the supply boiler, to be heated either by the steam passing through it,
after leaving the engine, or by passing the flue of the furnace through or
under it, after leaving the boiler. The supply pump brings the water up from
the well or stream, or if one be used, out of the condenser, forcing it into
the supply boiler, which it keeps always full, out of which it passes by a
small pipe into the principal boiler, and may be thus heated by the smoke flue,
to the same degree with the water in the boiler before it enters. This may
appear incredible, until we consider that the steam which works the engine,
carries off the heat from the boiler, which is not the case with the supply
boiler, from which no steam escapes. And as we may suppose that cold water receives
heat more freely than hot, we sometimes make our boilers in several separate
parts, passing the flue of the furnace through them all, and forcing our supply
water into that part farthest from the fire, to pass from one to the other by
small connecting pipes meeting the fire; on these principles we obtain a
greater quantity of heat from the fire into the water.
OF
THE CONDENSER.
THE weight of the
atmosphere resists the motion of the piston of our engine, when we work without
a condenser, with a power equal to 15 pounds to the inch of its area; the use
of the condenser is to take off this resistance, and is very useful when we
work with weak steam, (see No. 4 in the table, article 6.)
In its usual form
it consists of a metal vessel, air tight, immersed in cold water, to receive
the steam as it leaves the engine. The steam is first let in plentifully to
drive out all the air through a valve fixed for that purpose. A cock is then
opened to let a continual jet of cold water enter, meeting the steam, which it
condenses into water again, and forms a vacuum in the condenser for the steam
to enter freely, which takes off the resistance of the atmosphere from the
piston of the engine: and if the vacuum be made perfect, it increases the
effect of the engine 15 pounds for every inch area of the piston. But the air
which arises from the first boiling of water would immediately fill the
condenser, again destroy the vacuum and stop the engine; to keep the vacuum
perfect, therefore, the air pump becomes necessary to extract this air, as well
as the jet water, and that made by the condensed steam, and part of this water
is returned into the boiler to supply it, and as there is a continual admission
of fresh water by the jet, there is a continual generation of air, by boiling,
to obstruct the vacuum, also a continual accumulation of sediment, forming a
non-conductor of heat on the bottom of the boiler, which obstructs the passage
of the heat from the fire into the water, causing the boilers to burn out;
besides much trouble and expense in cleansing them.
To avoid all
which, we improve the condenser by making a jet vessel of metal, purposely for
receiving and cooling our jet water; immersing it in cold water, under or near
the condenser. Out of this vessel the jet rises into the condenser as before.
The air pump, which serves also for our supply pump, extracts the water and air
from the condenser, and forces back into the jet vessel as much water as it
will receive; keeping it always full; the residue (after the air is suffered to
escape through a valve for that purpose fixed in the top of an air vessel,
which is fixed in the pipe leading the water from the pump into the supply
boiler) is forced into the the boiler to supply it. A small air vessel is
attached to the jet vessel, the spring of which keeps up a continual jet. The
water enters the jet vessel at one end and the jet issues at the other, which
gives the water time to cool, to fit it for the purpose of condensing. By these
means we admit no fresh water, but continue to work with the same quantity with
which we begin; distilling it over and over repeatedly, we soon get rid of the
air, and our vacuum becomes more perfect: from water distilled many times over
no sediment can accumulate to cause our boilers to burn out, nor air to
obstruct our vacuum. Our boiler may be said to be inexhaustible, and will last
much longer, and require less fuel.
In some situations
it may suit better to make the condenser sufficiently capacious to expose so
much surface to cold water, as to condense the steam without a jet; laying it
in running water, and (when it can be done conveniently) so fixed that the
water can be turned off at pleasure, which would enable us to expel the air
more completely before we begin to work. The water formed by the steam in this
condenser being driven back into the supply boiler by the air pump, makes it
inexhaustible as before.
OF
THE VOLCANIC STEAM ENGINE.
IN our pursuit of
means to prevent the loss of the heat which is carried up the chimney of the
furnace, let us have recourse to the works of nature: view the natural
volcanoes, where the fire burns without the aid of atmospheric air; where all
the elastic fluid generated by the fire dissolving the fuel, (see article 4)
and all the steam formed by the water that may occasionally come in contact
with the fire, united, forms the most terrible and powerful of all steam
engines; in which the furnace, boiler, and working cylinder are united in one,
working on the simple principle of applying great elastic power; casting up
mountains, and making the earth quake as she brings her strokes. To apply these
principles as far as we can, we make a cylindric boiler, about 36 inches
diameter, 8 or 10 feet high, with a furnace inside of it 18 or 19 inches diameter.
Both the boiler and furnace are united to the same heads, the fire being inside
of the ivater, and the smoke-flue turned downwards through the water to the
bottom, where the smoke is vented and rises in many streams of small bubbles,
that it may impart all its heat to the water to generate steam. The elastic
fluid generated by the combustion of the fuel, which we may suppose is 2000
times the bulk of the fuel, and the air used to kindle the fire, expanded by
the heat to double its original bulk, unites with the increased quantity of
steam, to work the engine with great elastic power. But until we can discover a
fuel that will burn without the aid of atmospheric air, or until we can find
means for kindling the fire with a blast of highly rarefied steam, as may be
the case in volcanoes, we use a forcing air pump to force in air to kindle the
fire. This form of engine will work with much less fuel, and be much lighter
than any other. It would therefore be more suitable for boats or land
carriages, &c. I made a small boiler on this principle, which operated
favourably; but being weary of the trouble and expense of putting new
principles into practice, I declined the pursuit until better prospects open,
or a more favourable opportunity offers. *
*The fire will burn more freely in this furnace,
in proportion as the air is compressed round the fuel, for the same reason that
a candle burns brighter in the receiver of an air pump when the air is
condensed, and dimmer as it is exhausted.
When this
principle is put in operation, in addition to those already explained, I
conclude that all the principles of nature suited to aid us in working steam
engines, are taken in, excepting one which would enable us to work a steam
engine without fuel; which I conceive is only to be done by collecting the rays
of the sun to boil our water, to generate steam, which may be done by plain
mirrors and perhaps with much less expense, than may at present be supposed.**
It remains for us to improve in the application of those principles until we
discover others, if there be any.
**Many may think this idea chimerical, until they
consider that water exposed to the single perpendicular rays of the sun, in a
suitable vessel, will soon acquire the heat of human blood, 92 degrees,
notwithstanding the constant evaporation going on, which carries off the heat
as fast as generated. Experiments may determine how many single rays must be
collected to triple the heat, from 92 to 276 degrees in the water, which, by
the table, (art. 3)would produce steam of elastic power 60 pounds to the inch.
This would work a very powerful engine, to raise water in hot countries for
various purposes. The rays collected to a focus by a convex lens, 36 inches
diameter, produced a far greater degree of heat than any furnace ever had. How
many lens can we suppose would he necessary to boil water to work an engine?
But we need not go to the expense of lens; 100 plain mirrors containing each 9
superficial feet, and which might he constructed of 9 small glasses of one foot
each, fixed in a frame, may collect rays sufficient for a powerful engine. How
did Archimedes burn the fleet which invaded Syracuse?
I am fully of opinion that the time will come
when water will he raised in great quantities by the heat of the sun at a very
small expense, for various purposes; but the expense of such inventions cannot,
in many instances, he borne by those who have the mental powers to design them;
at least it is highly imprudent for them to risk it. In such cases aid from
government becomes necessary.
44
SCALE OF HEAT
From the
highest degree of heat produced in an air-furnace to the greatest degree of
cold hitherto known, which was produced at Hudson's Bay, in December 1784, by a
mixture of vitriolic acid and snow. See the American edition of the
Encyclopedia, vol.xviii.p.500.
|
|
Fahrenheit |
Wedgewoods's Scale |
|
Extremity of Wedgwood's scale |
3227.70 |
2400 |
|
Greatest heat of his small air-furnace |
2187.7 |
160 |
|
Cast iron melts |
1797.7 |
130 |
|
Greatest heat of a common smith's forge |
1732.7 |
125 |
|
Welding heat of iron, greatest |
1342.7 |
95 |
|
Welding heat of iron, least |
1277.7 |
90 |
|
Fine gold melts |
523.7 |
32 |
|
Fine silver melts |
471.7 |
28 |
|
Swedish copper melts |
458.7 |
27 |
|
Brass melts |
380.7 |
21 |
|
Heat by which his enamel colours are burnt on |
185.7 |
6 |
|
Red heat fully visible in day-light |
1077 |
1 |
|
Red heat fully visible in the dark |
947 |
0 |
|
MERCURY BOILS, also linseed and other expressed oils |
600 |
|
|
Oil of Turpentine boils |
560 |
|
|
Sulphuric acid boils |
546 |
|
|
Lead melts |
540 |
|
|
Lead melts |
460 |
|
|
Tin melts |
408 |
|
|
Sulphur melts |
244 |
|
|
Nitrous acid boils |
242 |
|
|
Cows' milk boils |
213 |
|
|
WATER BOILS |
212 |
|
|
Human urine boils |
206 |
|
|
Brandy boils |
190 |
|
|
Alcohol boils |
174 |
|
|
Serum of blood and white of eggs harden |
156 |
|
|
Bees-wax melts |
142 |
|
|
Heat of the air near Senegal sometimes |
111 |
|
|
Hens hatch eggs about |
108 |
|
|
Heat of birds from |
103 to 111 |
|
|
Heat of domestic quadrupeds from |
100 to103 |
|
|
Heat of the human body from |
92 to 99 |
|
|
Heat of a swarm of bees |
97 |
|
|
heat of the ocean under the equator |
80 |
|
|
Butter melts |
74 |
|
|
Vitriolic acid of the specific gravity of 1780 freezes at |
45 |
|
|
Oil of olives begins to congeal |
43 |
|
|
Heat of hedgehogs and marmots in a torpid state |
39.5 |
|
|
WATER FREEZES and snow melts |
32 |
|
|
Milk freezes |
30 |
|
|
Urine and common vinegar freeze |
28 |
|
|
Human blood freezes |
25 |
|
|
Strong wines freeze |
20 |
|
|
A mixture of one part of alcohol and three parts of water freezes |
7 |
|
|
A mixture of snow and salt freezes |
0 to 4 |
|
|
Brandy, or a mixture of equal parts of alcohol and water freezes |
7 |
|
|
Spirits of wine in Reaumur's thermometer froze at Torneo |
34 |
|
|
MERCURY FREEZES |
39 to 40 |
|
|
Cold produced by Mr. Macnab at Hudson's Bay, by a mixture of vitriolic acid and snow |
69 |
|
A
TABLE
Of the strength
of Metals ascertained by experiments; the weight hung to an inch bar, with a
straight pull. See the American edition of the Encyclopedia, vol. xvijj. p.10.
|
Metal |
|
lbs. |
|
Gold, cast |
|
20,000 |
|
|
|
24,000 |
|
Silver, cast |
|
40,000 |
|
|
|
43,000 |
|
Copper, cast |
Japan |
19,500 |
|
|
Barbary |
22,000 |
|
|
Hungary |
31,000 |
|
|
Angelsea |
34,000 |
|
|
Sweden |
37,000 |
|
Iron, cast |
|
42,000 |
|
|
|
59,000 |
|
Iron, bar |
Ordinary |
68,000 |
|
|
Stirian |
75,000 |
|
|
Best Swedish & Russian |
84,000 |
|
|
Horse Nails |
71,000 |
|
Steel, bar |
Soft |
120,000 |
|
|
Razor temper |
150,000 |
|
Tin, cast |
Malaca |
3,100 |
|
|
Banca |
3,600 |
|
|
Block |
3,800 |
|
|
English block |
5,200 |
|
|
English grain |
6,500 |
|
Lead, cast |
|
860 |
|
Regulus of antimony |
|
1,000 |
|
Zinc |
|
2,600 |
|
Bismuth |
|
2,900 |
|
Brass, a mixture of copper and zinc |
|
51,000 |
"The expansion
of bodies by heat is very various, and in solids does not seem to be guided by
any certain rule. In the forty-eighth volume of the Philosophical Transactions,
Mr. Smeaton has given a table of the expansions of many different substances,
from which the following particulars are extracted. The degree of heat employed
was 180 degrees of Fahrenheit's thermometer, and the expansion is expressed in
10,000th parts of an English inch."
|
Substance |
10,000th parts of an English inch |
|
A foot of white glass barometer tube |
100 |
|
Martial regulus of antimony |
130 |
|
Blistered steel |
138 |
|
Hard steel |
147 |
|
Iron |
151 |
|
Bismuth |
167 |
|
Hammered Copper |
204 |
|
A mixture of 3 parts of copper with 1 of tin |
218 |
|
Cast brass |
225 |
|
A mixture of 16 parts of brass with 1 of tin |
229 |
|
Brass wire |
232 |
|
Speculum metal |
232 |
|
Spelter solder, 2 parts brass and 1 zinc |
247 |
|
Fine pewter |
274 |
|
Grain Tin |
298 |
|
Soft solder, 2 parts lead and 1 tin |
301 |
|
A mixture of 8 parts of zinc and one of tin, a little hammered |
323 |
|
Lead |
344 |
|
Zinc or spelter |
353 |
|
Zinc hammered an inch per foot |
373 |
DIRECTIONS FOR WORKING A STEAM ENGINE ON THE
NEW PRINCIPLE.
It
has been shown that a vacuum will probably receive and contain a greater
quantity of heat in a latent state than a plenum, (see article 4): and it is
evident that the piston of an engine leaves a perfect vacuum behind it in the
cylinder at every stroke, which is to be filled with latent heat from the fire,
besides active heat to give power to the steam to carry its load; now it
appears plain, that if the engine be started before the steam has acquired a
sufficient power, and let it move briskly with the load it is'able to carry,
that the piston will create vacua so fast, as to carry off all the heat of the
fire, as fast as generated, to supply the latent heat to fill the vacuum: it
will therefore be very difficult to use the power of the steam to its proper degree,
and thus fuel may be consumed without producing the desired effect. To save the
fuel retain and confine the steam in the boiler until the power is raised to a
greater degree than is sufficient to carry the load, which will be shown by the
lifting of the safety valve with the weight farther from the centre than it is
commonly hung; then start the engine, and the power will be reduced to its
proper degree before the cylinder becomes hot; take care that the engine does
not dart with too quick a motion, and it will carry off less heat in a latent
state at every stroke, but more in an active state, producing power in the
steam to carry its load, and the engine will work on, if the fire be kept up,
and produce great effects.
If
propelling a boat against the Mississippi, fix the valve to shut off quick, say
at 1/6 or 1/4 part of the stroke, when in an eddy or slow current; let the
supply pump work to fill the boiler, and augment by these means the elastic
power of the steam so as to be ready to lift the safety valve with a double
load by the time you arrive at the strongest current; to ascend which alter the
valve to shut off at 1/2 the stroke, and stop the supply pump until you have
passed the rapid, (see article 8,) and the power of the engine will be quadrupled,
which may be kept up by increasing the fire until you surmount the difficulty:
you may regulate the power by closing and opening the throttle valve to let
more or less steam out of the boiler into the cylinder; but there will be a
great loss of power this way, because it would be working with weak steam in
the cylinder while you have strong in the boiler, and returning to the old
exploded principle.
If
propelling a land carriage, on turnpike roads, while on level or descending
ground, gear the wheels to move forward quickly, and fill the boiler, reserving
the steam, as above stated; so as to quadruple the power of the engine by the
time you arrive at the foot of a hill; then alter the gears to move the
carriage with or 1/2 velocity, as the ascent may require, and you ascend with 8
or 16 times the power, with 21 or 1/4 velocity, which enables you to ascend any
hill on which the wheels will not slide. If the driver of a 5 horse wagon could
have at his command 75 more to hitch on to help him, he would easily ascend
hills. At all steady work, such as grinding, sawing, &c. fix the valves to
shut off so as to keep up the power in the boiler and you will produce much
greater effects from the same consumption of fuel, (see article 4.)
These
principles have been proven as follows:
I
constructed for the Board of Health of Philadelphia a machine for cleaning
docks, called the Orukter Amphibilos or Amphibious Digger. It consisted of a
heavy flat bottomed boat, 30 feet long and 12 feet broad, with a chain of
buckets to bring up the mud, and hooks to clear away sticks, stones, and other
obstacles. These buckets are wrought by a small steam engine set in the boat,
the cylinder of which is 5 inches diameter and the length of stroke 19 inches.
This machine was constructed at my shop, 1 1/2 miles from the river Schuylkill
where she was launched. She sunk 19 inches, displacing 551 cubic feet of water,
which at 62.5 pounds, the weight of a cubic foot, gives the weight of the boat
34,437 pounds, which divided by 213, the weight of a barrel of flour, gives the
weight of 161 barrels of flour that the boat and engine is equal to. Add to
this the heavy pieces of timber and wheels used in transporting her, and the
number of persons genelally in her, will make the whole burden equal to at
least 200 barrels of flour. Yet this small engine moved so great a burden, with
a gentle motion up Market.street and around the Centre Square; and we concluded
from the experiment, that the engine was able to rise any ascent allowed by law
on turnpike roads, which is not more than 4 degrees.
When
she was launched we fixed a simple wheel at her stern to propel her through the
water by the engine. Although she is square at each end and fully constructed
for sailing, (excepting that she is turned up short at bottom) and drew 19
inches water, yet we concluded diat if the power had been applied to give the
paddle wheel the proper motion we could have stemmed the tide of the Delaware.
It has been ascertained by accurate experiments,* that a boat formed to the
proper angle at her bow and stern, will pass much easier through the water than
one formed as this was; and that the increase of length does not sensibly
increase the resistance: we may therefore safely conclude, that an engine 4
times as powefful would propel a boat 16 feet wide, 90 feet long drawing 2 feet
water, the weight of which would be 86 tons, equal to 903 barrels of flour,
about 7 or 8 miles an hour through the water, every thing being properly and
well constructed. This force would be sufficient to propel the like burden
against the stream of the Mississippi at the rate of 4 miles an hour.
Considering the temporary manner in which the works were constructed for this
experiment of propelling the Orukter both by land and water; the great friction
there was to be overcome, and the disproportion of the load to the engine,
there cannot remain any doubt but that a steam carriage may be constructed to
carry 100 barrels of flour 50 miles in 24 hours, on any well made and well
regulated turnpike road; and when every thing is properly arranged for
supplying the machine with water and fuel at proper stages, one such carriage
will clear as much net profit as 10 five horse waggons. Conceiving that those
who are proprietors of turnpike roads are the only persons whose interest
directs them to engage in the enterprise, I made the following statement, to be
laid before the managers of the Philadelphia and Lancaster Turnpike Company.
*See
the American edition of the Encyclopedia, vol. xvi. art.
"Resistance."
TO THE LANCASTER TURNPIKE ROAD COMPANY:
GENTLEMEN,
PERMIT me to lay before your respectable body
the following statement.
I conceive that carriages may be constructed,
to be propelled by the power of steam engines which I have invented, to
transport merchandise and produce from Philadelphia to Columbia, and from
thence to Philadelphia, much cheaper than can be done by the use of cattle.
|
|
Dollars |
|
The engine I estimate at |
1500 |
|
The carriage |
500 |
|
Say for unforeseen expenses |
500 |
|
Total |
2500 |
This carriage I allow to carry 100 barrels of
flour, and to travel 3 miles per hour on level roads, and 1 mile per hour up
and down hills; say about 40 miles per 24 hours; making a trip from Columbia to
Philadelphia in 2 days.
It requires
5 horse wagons, of S horses each, to transport 100 barrels the same distance in
3 days. The expense I estimate as follows:
|
|
Dollars |
|
5 Horse wagons at the cheapest rate, 100 dolls. each |
500 |
|
25 horses at 100 dolls. each |
2500 |
|
Gears for 25 horses at 7.75 dolls. |
193.75 |
|
5 waggon covers at 7 dolls. |
35 |
|
30 bags for feed at 1 doll. |
30 |
|
5 jack screws at 6 dolls. |
30 |
|
5 whips at 75 cents |
3.75 |
|
5 feed troughs at 2 dolls. |
10 |
|
5 grease cans at 33 cents |
1.65 |
|
|
3304.15 |
|
Expense of the steam wagon |
2500 |
|
|
2500 |
|
First cost in favour of the steam wagon, exclusive of the drivers |
804.15 |
|
The steam wagon will perform the journey in two days, and carry 100 barrels of flour at 1 doll. 25 cents |
125 |
|
The expense of fuel, 20 bushels of coals per 24 hours, 40 bushels at 37 1/2 cents, or wood equal thereto |
15 |
|
3 men at 1 doll. per day for 2 days |
6 |
|
|
21 |
|
Profits of the steam wagon per journey, or 52 dollars per day |
104 |
|
The horse wagons will perform the journey in three days and carry 100 barrels at 1 doll. 25 cents |
125 |
|
The expense of feed for 25 horses at 33 1/3 cents per day, 3 days |
25 |
|
5 men drivers at 1 doll. |
15 |
|
|
40 |
|
Profits on 1 journey, 85 dolls. which is 28 dolls. 33 cents per day |
85 |
The expenses of repairs, of horses, wagons, and
gears of each horse wagon will be fully equal to the repairs of the steam
wagon.
|
|
Dollars |
|
From the profits of the steam wagon per day |
52 |
|
Deduct for repairs |
2 |
|
Nett profit of the steam wagon per day |
50 |
|
From the profits of the 5 horse wagons per day |
28.33 |
|
Deduct for each 2 dolls. |
10 |
|
Net profit of all the 5 horse wagons per day, or 3.66 dolls. each per day |
18.33 |
Add to all this that
the steam wagon consumes nothing while standing, will roll and mend the roads,
while the horse wagons will cut them up.
Upon the whole it appears that no competition
could exist between the two. The steam wagons would take all the business on
the turnpike roads.
I have no doubt but you will duly appreciate
the importance of such an improvement, and conceive it to be your interest to
appropriate the sum necessary to put it in operation. I have invented the only
engine that will answer that great purpose, as well as many others for which
power may be wanted.
It is too much for an individual to put in
operation every improvement which he may be able to conceive and invent.
I have no doubt but
that my engines will propel boats against the current of the Mississippi, and
wagons on turnpike roads with great profit. I now call upon those whose
interest it is to carry this invention into effect. All which I respectfully
submit to your consideration.
Your
obedient humble servant,
OLIVER
EVANS.
Philadelphia,
Sept.
26th,
1804
OF PROPORTIONING THE CYLINDER TO THE BOILER
IN THE CONSTRUCTION OF STEAM ENGINES.
THE
limits of this work will not admit of full directions for constructing steam
engines: but the engineer must be guided by very different principles in his
arrangement of a steam engine, to be wrought on the new principles already laid
down, from those which should guide him, in arranging one to be wrought by
atmospheric steam, where, the larger the cylinder, provided the boiler be
sufficient to fill it with steam at every stroke, the more powerful the engine,
while the reverse is the fact in this case, viz. The less the cylinder through
which all the steam the boiler will make, is made to pass, the more powerful
the engine, and the greater the effects it will produce, provided the boiler be
strong enough to contain the power of the steam. Doubling the diameter of the
cylinder doubles the friction, and quadruples the resistance of the atmosphere;
it also quadruples the vacuum formed behind the piston, requiring to be filled
with latent heat at every stroke, (see article 12.)
To
show this more clearly by an example: Suppose we had an engine, on the new
principle, arranged so that the boiler would supply the cylinder of 30 inches
area, with steam of power 120 pounds to the inch. Then 30 multiplied by 120 is
equal to 3600 pounds, the load; but suppose the friction of the piston to b(
150 pounds, added to 450 pounds, the resistance of the atmosphere, makes 600
pounds which taken from 3600 pounds leaves 3000 pounds, the nett load the
engine will carry.
Then
suppose we enlarge the cylinder to double the diameter, which doubles the
friction to 300 pounds, and quadruples the resistance of the atmosphere to 1800
pounds, making 2100 pounds, total resistance. The area of the cylinder, 120
inches, multiplied by 1/4 the power, reduced now to 30 pounds to the inch by
the Boylean law (see articles 4 and 6) is equal to 3600 pounds, the load; from
which take the increased resistance, 2100 pounds, leaves 1500 pounds for the
net load of the enlarged cylinder; just half the load of the small one. But
this is supposing the Boylean law to hold true with regard to steam, and that
it is a permanent elastic fluid, which it is not. When we consider that the
vacuum formed behind the piston (see article 12) was quadrupled also by
doubling the diameter of the cylinder, and would probably absorb all the heat
in a latent state, we may safely infer, that the cylinder enlarged, would not
overcome the resistance of the atmosphere and friction, and would therefore
carry no load at all, provided the piston moves with equal velocity in each
case.
The
power of a man is equal to raising 30 pounds 2 1/2 miles per hour, 8 or 10 hours
in 24; and the power of a horse is equal to 5 men, or equal to raising 150
pounds 2,1 miles or 13200 feet per hour. This has been ascertained by many
experiments, and long established as data on which to found our calculations.
Then, to ascertain the diameter of a cylinder and length of stroke, to produce
a given power; 13200 feet per hour, divided by 60 is equal to 220 feet per
minute, the velocity of the piston. Suppose we take 36 for the number of
strokes the engine is to strike per minute; then 220 feet divided by 36 quotes
6.1 feet for the length of the double stroke, say 6 feet; that is 3 feet length
of stroke, 36 down and 36 up strokes per minute to make the piston pass about 2
1/2 miles per hour.
Suppose
again the piston to carry an average load equal to 50 pounds to the inch
instead of 80 pounds, to make allowances, (see article 6), then every 3 inches
area of the piston is equal to a horse's power.
The
side of a square being 1, the diameter of a circle of equal area is 1 128/1000:
therefore to find the diameter of the cylinder for any number of horse's power
take the following
RULE.
Multiply
the number of horses by 3, extract the square root and multiply by 1 128/1000:
the product will be the diameter of the cylinder, 3 feet length of stroke, 36 strokes
per minute.
The
diameter of a circle being 1, the side of a square of equal area will be
7854/10000 therefore to find the area of any cylinder, multiply the square of
the diameter by .7854 of a decimal and the product is the area.
To
produce the power of a horse, a piston 3 inches area must move 220 feet, or
2640 inches per minute, with a load of 150 pounds; and 2640 multiplied by 3 is
equal to 7920 cubic inches of space the piston forms into a perfect vacuum
behind it per minute to be filled by the heat, (see article 12.) Therefore to
find the power of any engine, multiply the area of the piston by the length of
stroke in inches and by the number of strokes per minute, and the product is
the space it passes through, or the vacuum it forms behind it; which divided by
7920 quotes the number of horses' power, when the piston carries an average
load of 50 pounds to the inch area.
To
find the number of strokes an engine must strike per minute to produce any
number of horses' power, multiply the number of horses' power by 7920, and
divide by the cubic inches of space the piston passes through at one stroke,
the quotient is the number of strokes the engine must strike per minute,
carrying 50 pounds to the inch area.
A
horse can work only 8 hours steadily in 24, therefore 3 relays are necessary,
and an engine of 10 horses' power will do the work of 3 times 10, equal to 30
horses.
Bolton
and Watt's best steam engines, on what I call the old principle, require 1
bushel of the best New Castle coals, from Walker's pits, (England) to do the
work of a horse per day. It has been shown (article 6) that my new principle
will produce at least 3 times the effect from equal fuel; one bushel of coals
to do the work of 3 horses; and can be built at half the price.
COMPARATIVE STATEMENT
Of the cost of building and expense of working
two steam engines, 10 years, the one on the old and the other on the new
principle.
|
|
Dollars |
Dollars |
|
Suppose an engine on the old principle to cost |
|
10,000 |
|
Interest at 6 per cent. 10 years |
|
6,000 |
|
Will consume about 60 bushels of coals at 33 1/3 cents, per day, 300 days per year, 10 years |
|
60,000 |
|
|
|
76,000 |
|
An engine of equal power, on the new principle will cost |
5,000 |
|
|
Interest 10 years |
3,000 |
|
|
Coals for 10 years will be about one-third the consumption |
20,000 |
|
|
|
|
28,000 |
|
|
|
48,000 |
This
difference is worthy the attention of those who wish to use steam engines.
A TABLE
Of the areas of cylinders of steam engines to
produce different powers with 3 feet length of stroke, 36 strokes per minute,
carrying an average load of 50 lbs. to the inch area.
|
Number of Horses' power, or bushels of wheat the power will grind per hour |
Area in inches |
Diameter in inches and decimal parts |
Number of horses that the engine will do the work of per day of 24 hours |
|
1 |
3 |
1.92 |
3 |
|
2 |
6 |
2.76 |
6 |
|
4 |
12 |
3.9 |
12 |
|
6 |
18 |
4.79 |
18 |
|
8 |
24 |
5.53 |
24 |
|
10 |
30 |
6.18 |
30 |
|
12 |
36 |
6.77 |
36 |
|
14 |
42 |
7.3 |
42 |
|
16 |
48 |
7.81 |
48 |
|
18 |
54 |
8.28 |
54 |
|
20 |
60 |
8.74 |
60 |
|
22 |
66 |
9.16 |
66 |
|
24 |
72 |
9.57 |
72 |
|
26 |
78 |
9.96 |
78 |
|
28 |
84 |
10.3 |
84 |
|
30 |
90 |
10.7 |
90 |
|
35 |
105 |
11.94 |
105 |
|
40 |
120 |
12.36 |
120 |
|
50 |
150 |
13.82 |
150 |
|
60 |
180 |
14.47 |
180 |
|
70 |
210 |
16.31 |
210 |
|
80 |
240 |
17.48 |
240 |
|
90 |
270 |
18.54 |
270 |
|
100 |
300 |
19.54 |
300 |
OF DISTILLATION.
A
KNOWLEDGE of
the principles already stated, (see article 4) leads us to discover an
improvement on distillation. When we consider that water and spirits may be
prevented from boiling, by increasing the pressure on their surface, and that
by boiling under a great pressure a much greater quantity of the fluid is
raised by equal quantities of heat in a state of vapour, and much less fuel is
used to obtain equal quantities of the fluid by raising it into vapour and
condensing it again, as in distillation, and that spirits boil at a less degree
of heat or under a greater pressure than water, we can by in creasing the
pressure on the liquid in the still, suppress the watery vapour until the
spiritous vapour rises rapidly. The essential oil which gives a bad flavour to
spirits may perhaps be suppressed in the same way, and the spirits brought off
pure at the first distillation, with much less fuel, by a rapid process. To
this improvement another may be added, to make the operation perpetual, by
constructing the still of a cylindric form, letting the beer in at one end, and
the dregs out at the other, in a continual stream; the spirits are extracted
during the passage: the operation may thus be continued at pleasure.
If
any person is willing to bear the expense and fatigue of the experiments, to
put this improvement into complete operation, he will find a full
specification, with explanations and drawings thereof, filed in the Secre-tary
of State's Office (called the Patent Office) of the United States. As a
compensation for such trouble and expense, I am willing to contract with such
person, in writing to be legally executed, to convey one half of the exclusive
right of using and selling, to be used, the said improvements.
OF VIBRATING MOTIONS OF MACHINERY.
FEW
mechanicians have considered what power is expended in giving quick vibrations
to heavy parts of machinery; such as saw gates, engine beams, &c. Writers
on the principles of mechanics have generally agreed in laying down as an axiom
that the weight of a body in motion multiplied into its velocity is a true
measure of its momentum: but few have informed us that the weight of a body
multiplied into the square of its velocity is the true measure of the effects
it will produce; which is the truth.* We are thus frequently led into great
errors, and to suppose that a double impulse will give double velocity to a
body; whereas a quadruple impulse is required to give double velocity; and if
so, a quadruple resistance is required to check a double velocity,**
consequently the power required to produce vibrating motions, is, as the
squares of their velocities multiplied into the weight of the bodies moved.
Aware of those principles, I have guarded against the use of the heavy lever
beam in the construction of my steam engines; as by an injudicious arrangement
nearly the whole power of the engine may be expended in giving a quick motion
to a heavy beam. The natural vibrations of a beam are regulated by its length
as much as those of a pendulum; and if we attempt to vary this motion to a
quicker one we expend much of the power of the engine to do it. I know no
better way of explaining this than by the laws of spouting fluids.*** Suppose water
to issue from under a head of 1 foot; it moves with that power 8.1 feet per
second: here, a power equal to 1/8 of the weight of the body moved is expended
to give that velocity. Suppose water to issue from under a head of 4 feet; it
moves with that power 16.2 feet per second: in this case, a power equal to 1/4
the weight of the body moved is expended to give it velocity. If it issues from
under a head of 16 feet it moves with velocity 34.4 feet per second, and a
power equal to 1/2 the weight of the body is expended to give it velocity. If
it issues from under a head of 64 feet, its velocity is 64 feet per second:
here the power expended to produce the motion is equal to the weight of the
body moved. But as an equal power is required to check the motion, therefore to
give a body a vibrating motion equal to 32.4 feet per second, requires a power
equal to the weight of that body, and 64.8 feet per second requires a power
equal to double the weight of that body.
*See
the Millwright's Guide, art. 6.
**Ibid.
***See
the Millwright's Guide, art.45.
Great
as this evil may appear, yet in most cases it almost entirely vanishes, where
the vibrations are produced by the revolutions of that simple instrument, the
crank, attached to the axis of a wheel, to which thepower is applied, as in the
constriction of saw-mills; where the power is applied immediately to move the
vibrating body attached by a connecting rod to a crank on the axis of which is
put a heavy fly wheel, as in steam engines without lever beams. In both cases,
the line of vibration continued, should pass through the centre of the circle
described by the crank, coinciding with the diameter of the circle. In the case
of saw-mills where the power is applied to the wheel and the crank moves the
saw, while the crank is receding from the vibrating line, it moves the saw with
a very gradual accelerated motion, and as it approaches the line of vibration
it retards the motion again as gradually. If the saw is not applied to do work,
the momentum communicated to it and its frame by the crank in giving the motion
is recommunicated or returned to the crank during the retarded motion;
therefore very little power will be required to keep up this vibrating motion.
While the saw is cutting, the momentum is expended performing the work. In the
ease of steam engines, the reverse takes place, the power being immediately
applied to produce the vibrating motion in the piston, which communicates
momentum to the fly wheel, while the crank recedes from the vibrating line; and
the momentum communicated to the piston and all attached to it is communicated
to the fly wheel, while the crank approaches that line, and very little power
is required to keep up this vibrating motion, without producing any other
effect. When the engine is at work, the power is expended to produce the
effects, and the momentum of the fly wheel regulates the motion and carries the
crank past the vibrating line, (where it would stop) and brings it to a
position to receive the power from the vibrating motion to keep up the circu1ar
motion of the fly.
The
late ingenious Robert Leslie of Philadelphia, to whose memory and judgment
great deference ought to be paid, was of opinion that the case is widely
different when moving a heavy lever beam past its natural vibrating velocity,
although it be attached to a crank.* We know that if the beam be nicely poised
but little power is required to cause it to vibrate with its natural motion,
which is as exactly governed by fixed principles as the vibrations of a
pendulum; but what power is required to give it any greater number of
vibrations per minute proportionate to its length and weight, I have not known
to be ascertained; nor can I say whether or not the momentum received from the
crank, while it recedes from the vibrating line, will be returned to it, with
the same exactness, while approaching that line as has already been stated, but
I am inclined to believe it will not. My ideas are not mature on the subject,
not having given it a full investigation, although 1 think it important.
*I
was well acquainted with Mr.Leslie. He was generally correct in his ideas of
the principles of mechanics, and made many useful discoveries and improvements.
DESCRIPTION OF A STEAM ENGINE ON THE NEW
PRINCIPLE.
EXPLANATION OF PLATE I.
PLATE
I. represents a perpendicular section of the different parts of a steam engine
on the new principle explained in this work, but they are differently arranged
in the construction.
a The end view of the
boiler, consisting of two cylindrical tubes, the best form for holding a great
power, the lesser inside of the greater. The fire is kindled in the inner one,
which serves as a furnace, the water being between them. The smoke passing to
the other end, is turned under the supply boiler, b, to heat the water for
supplying the waste occasioned by working; c the supply pump, which
brings water up, and forces it into the supply boiler, at every stroke of the
engine.
The
steam ascends the pipe, and if the throttle valve d be lifted to let the
steam into the engine, and valves e and f be opened, the steam drives the piston g to the lower end of the
cylinder, as it appears in the plate, the steam escaping before the piston
through the valve f. As soon as the piston is down the valves e, f shut and h, i open, the steam enters
at h to drive the piston up again, and escapes before the piston through the
valve i. These
4 valves are wrought by 2 wheels, k, l with cams on their sides, which strike
against 4 levers, not shown in the plate, to which the stems of the valves are
attached, and which open and shut them at the proper time. The motion of the
piston g
gives motion to the lever m-n; and the rod m-o, connected to the
crank, puts it in motion, and the fly wheel q-r keeps its motion
regular; the spur wheels s- t, of equal size, move the valve wheels l- k; the lever m-n works the supply pump c. Thus the motion is
continued, and the cog wheel v of 66 cogs going into the tunnel u of 23 cogs, gives the
stone w
100 revolutions per minute, when the piston strikes 35 strokes. This cog wheel
may move any other work, or instead thereof a crank may move a pump or saw, as
this engine may be made to strike from 10 to 100 strokes per minute, as the
ease may require; and if the working cylinder be 8 inches diameter, it will
drive a pair of 5 feet millstones, or other work requiring an equal power.
The
steam, after it leaves the engine, escapes up the pipe x-x, through the roof of
the house, or into a condenser, if one be used, or through the supply boiler to
heat the water.
y
A safety valve, kept down by a lever graduated like a steelyard, to weigh the
power of the steam; this valve will lift and let the steam escape, when its
power is too great.
If
the pipe of the safety valve be turned into the flue of the furnace, then, by
lifting the valve, the ashes may be blown out of the flue.
This
engine is of a simple construction, easily executed by ordinary mechanics: the
valve seats are formed by simple plates, with holes in them and are easily
cast.
In
working this engine to drive ten saws, we find that if we put her in motion as
soon as she has power to drive one saw, and suffer her to move briskly, she
carries off the heat from the boiler nearly as fast as it is generated, and fuel
may be consumed and time spent to little purpose; but if we confine and retain
the steam in the boiler, until it lifts the safety valve with a power
sufficient to drive ten saws, she will start with that load, and carry it all
day, and consume but little more fuel.
It
takes up but little room in the building. The draught is drawn from half an
inch to a foot, except the millstones, and two wheels that move them; they are
a quarter of an inch to a foot.
70
EXPLANATION
OF THE SCREW MILL INVENTED AND PATENTED BY THE AUTHOR.
This
mill is intended for breaking all hard substances, and to prepare them for
entering millstones to be pulverized.
No.1 Plate II. is a perpendicular section of
the mill with the screw set horizontally, which has been found the best
position.
A B the screw,
which is for breaking plaster at the rate of 2 tons per hour, is made by
twisting a flat iron bar 5 or 6 inches broad, 1 1/2 inch thick, making the
screw part 12 or 15 inches long. It is set to revolve about 40 times in a
minute, over a grate fixed in the bottom of a hopper strongly made and plated
inside with iron; the upper corner of the bars of the grate next to A is made
highest, to catch against the lumps of plaster, to prevent them from slipping
too freely before the screw, which is made to turn so as to drive the plaster
towards B, and causes the screw to press hard against the steel plate A, fixed
there to keep the screw steady to its place. The plaster, in large lumps, is
thrown into the hopper at C, and broken by the stroke of a large hammer, so
that the screw will take hold of it, and as it is broken by the screw it falls
through the grate D, and is guided by a sloping spout B E into the millstones,
or into an elevator, to be raised to the millstone hopper. A screen may be set
inthe bottom of this spout to let all that the screw makes sufficiently fine,
pass through, to be guided by a second bottom F to the proper place, without
passing through the stones.
G H a fly wheel on
the shaft, connected with the screw to give it motion. This fly is necessary to
regulate the motion of the screw, and by its momentum to overcome all extra
resistance, occasioned by large or hard lumps, and to equalise the stress on
the cogs of the wheels which give the motion.
No.2 represents a
perpendicular plane section of a screw mill with the screw set perpendicular,
to revolve in a hopper closed at bottom so as not to suffer lumps of too large
a size to pass through. The bottom part of this hopper may be made of cast iron
fluted or furrowed, so as to prevent the substances, to be broken, from sliding
round with the screw; or it may be open, in form of a grate, to let the lumps
pass through, when sufficiently reduced. Or a hole may be made in a stone to
form the lower part of the hopper. Or the upper millstone may be made
stationary, and the lower one made fast to the screw, to turn and perform the
grinding in this case, the eye of the upper stone forms the lower part of the
hopper. Or the millstone may be set vertically, instead of horizontally, and
the screw set horizontally to run in a hopper but without a grate, as in No.1,
the screw passing through the eye of the stationary stone, and made fast to the
running one, then turning the screw turns the stone, and the screw drives the
substance as broken, through the eye of the stationary stone, in between them
to be ground, which does very
well. I made a hand mill on this simple structure, with which I had several
thousand bushels of plaster ground by hand; it is perhaps the best hand mill for
that purpose: the running stone is much larger than the stationary one, and
serves the purpose of a fly. This mill I sold for the purpose of breaking
charcoal for a steel furnace, for which it answers very well. The millstone is
fixed at the end A, and the crank put on B, and turned so as to drive the
plaster or coal, &c. as broken between the stones: its simplicity renders
it the more useful; it has neither wheel nor cog belonging to it: * or the
screw may be attached to the cock head of the spindle of the millstone, when
fixed in the common way, and a hopper put round the screw to break the hard
substance and let it fall into the eye of the stone. This screw mill may be
changed into a great variety of forms and be still on the same principle and be
a good machine: but perhaps no form will be found better than No. 1, for
breaking plaster, charcoal, Indian corn in the ear, to grind the cob with the
grain, for food fot cattle, several kinds of paints, lead and other ores,
different kinds of barks, &c. and perhaps no cheaper and more simple
machine can be invented for a variety of such purposes.
*This
invention I made and reduced to practice during the winter of 1795-6. It was
with difficulty I could find any person willing to apply it to water-mills.
Several years passed before I could prevail with any one to try it. Mr. John
Rhynehart of Chester county was the first to adopt it; and when he got it a
going, he came and advised me to take out a patent immediately, saying, it was
an excellent machine; it answered so well for breaking plaster, and also Indian
corn, with which people came considerable distances with waggon loads to get
ground for their cattle. It is now getting into pretty general use, and there
has at least a dozen of inventors started up already, all claiming the
invention; so easy is it to invent a machine already in use.
Those
who may wish either to make or use the said mill, may obtain permission by
applying by letter directed to the inventor in Philadelphia, on paying 10
dollars for the license, for common uses. And those who make or use said mill,
and refuse or neglect to pay for a license, will be treated as the act of
congress in such cases made and provided directs.
USEFUL INVENTIONS BV DIFFERENT PERSONS.
PLATE
III represents a front view of the patent Straw-cutter, invented and improved
by Moses Coates and Evan Evarts. The principle of this improvement, secured by
the patentees, is in hanging the knife on four centres or joints, at a proper
angle, in such position as to slide the edge across the straw at the same time
that it is pressed down through it, which causes it to cut with much more ease
than in the common way. This is the principal improvement, and is well worthy
the notice of those who have much straw to cut, as it can be done with less
than half the labour of the mode now in use. Thev have also made several other
improvements on the machine, viz. in the apparatus for moving the straw
forward, and in fixing the knife to be worked by both hands, &c. as appears
by the drawing and explanations given by the inventors themselves. Thev
sometimes form the steel of this machine aslant so as to cause the knife to cut
off the straw at an angle of about 45 degrees, which makes it etit much easier
than at right angles, or square across.
EXPLANATION OF THE PLATE.
I.
OF THE STRAW-CUTTER.
B
B a board screwed to the feet.
K
K the knife screwed to a board.
C
C the connecting bars.
H
I the hold-fast, 2 pieces beveled to draw the knife to the steel ; the
connecting bars set between them.
L
the handle of the knife. The knife must be ground strait on the side next the
steel.
D
A the drag that moves the straw.
R
the under roller and a fork. There are 6 iron plates set edgewise in the under
roller which is fixed under the box, to come through the bottom board one inch:
there are also 6 iron plates on an upper roller with 27 crooked forks fixed in
them, with the round part foremost that they may clear themselves from the
straw as the roller turns to push it forward.
G
another part o£ the drag put on the end A which is raised by a pin in the lower
connecting bar and gives motion to the drag.
The
rollers are set 17 inches from the steel; a frame is hung to the upper roller
with a weight of 30 pounds attached to it, to press it on the straw, and it is
raised or lowered by a lever hung under the box.
A
strip of hard wood, dressed beveling and put on the front part of the box, for
the lower end of the knife to slide on, will bear the upper end of the knife to
the steel, and cut clean. At the instant you raise the knife raise or draw your
foot from the treadle that the straw may move forward at the same time. It will
cut 100 square inches at one cut. It is well calculated to cut corn-fodder for
cattle.
The
irons may be had, or smiths may obtain the privilege of making them from either
of the following mentioned persons: Oliver Evans, Philadelphia; William Morgan,
Georgetown, Potomac; George Worral, Lancaster; Moses Coates, Chester county, or
Evan Evans, City of Washington.
II. OF THE FLOUR-PRESS.
No.2
represents an elevation of the Flour-press, invented, improved and patented by
----Clarke and Evan Evans. The principle secured by the patent is in fixing the
fulcrum of the lever to be moveable instead of stationary as is common. The
long arm of the lever lengthens and the short arm shortens during the whole
operation of pressing, which causes the power to increase with the resistance.
The machine works quick while it meets with little resistance, and powerful
when the resistance is increased. Time is not unnecessarily expended, as a
barrel of flour can be packed by it in half a minute. This is the principal
improvement of the invention, and is well worthy the attention of millers.
A
the barrel of flour.
B
the funnel.
C
D the driver.
E
F the lever.
G
H the connecting bars, fastened by a strong pin to each side of the lever at G,
and to the driver at H.
I
two strong posts put through the floor, and keyed below the joists at K.
The
lever works between them on a strong pin L, and when brought down by the hand,
moves the pin G, in the dotted circle I, and the connecting bars draw down the
driver C, forcing the flour into the barrel; and as it becomes harder packed,
the power of the machine increases, as the pin G, approaches the posts I. The
under sliding part of the lever is drawn out to increase its length, and is
assisted in rising by the weight M, fastened to a line passing over the pulleys
N
O. When the pin G is brought down within half an inch of the centre of the
posts or plumb line, the power increases from 1 to 288; and with the aid of a
simple wheel and axis, say the difference between the wheel and axis is as 1 to
15, from 288 to 8640; that is to say, one man will press as hard with this
machine as 8640 men could do with their natural strength. It is extremely well
calculated for a printing press, cotton, tobacco, cyder, or, in short, any
thing that requires a powerful press.
CERTIFICATE.
We
do certify that we have proven the above packing machine,
and
find its principles to be such, that the power increases with the resistance,
so as to render it a most excellent machine for packing flour with ease and
despatch. It is simple and cheap in its structure.
OLIVER
EVANS,
CHARLES
TAYLOR, Engineer.
The
above Machines can be seen at Oliver Evans's flour-store, corner of Ninth and
Market streets, Philadelphia, or at William Morgan's Georgetown, Potomac, at
either of which places, or of George Worral, Lancaster, Moses Coates, Chester
county, or the subscriber, City of Washington, may be purchased the privilege
for the Straw-cutter, for four dollars; and the Press for flour at the
following rates: One run of stones, ten dollars; two ditto, seventeen dollars ;
three ditto, twenty-two dollars; four ditto, twenty-seven dollars, and eight
ditto, fifty-four dollars.
Those who infringe on the patents will be dealt
with as the act of congress directs.
MACHINE FOR REMOVING EARTH.
As
no greater improvements have ever been made in any country than those of
navigable canals and turn-pike roads, many of which remain to be made in this
country, I have given a plate and description of a machine, invented and
improved by Gershom Johnson, for removing earth short distances, by the force
of cattle, which has proved very useful for that purpose. The inventor asserts
that with this machine, drawn by three horses, he can do more work than 20
men.*
*Fortunately for the inventor, he did not take out his
patent when he paid his money into the patent office; if he had done so, his
term would now have been nearly expired, without having yielded him any
emoluments equal to his expense and attention. The spirit for improvement in
making turnpike roads and canals which prevails at this time will call for the
use of this machine, and he will probably be well rewarded.
Plate
IV (unavailable) represents a side view of the machine.
B
E the box for holding the earth, fixed to theshovel which scoops it up. B the
edge of the shovel, made of sheet-iron, 4 feet wide, strengthened by a steel
plate in front 8 inches wide. R a piece of timber to strengthen the shovel. Q
one of the hind wheels. F one of the handles. G a treadle. H a chain connecting
the treadle to the handle. I one of the iron bars connecting the shovel to the
axel of the fore wheels L.
THE OPERATION.
The
cattle are hitched to the bars I, and the man at the hadnles guides the point
of the shovel B between the solid and loose earth to scoop up a load, driving a
quantity before the shovel. If the load proves too heavy he puts his foot on
the treadle and raises the point of the shovel B a little, which causes it to
drop part of the load, especially in hollow places; and when the machine
arrives at the place where the load is to be deposited, he throws up the
handles suddenly which drives the shovel into the solid earth, and the force of
the cattle turns the shovel over, bottom up, the bar N to rest on the iron bars
I, and discharges the load. The shovel remains in this position, the bars O
sliding on the ground, until the machine arrives at the place to take up
another load, when by the rope P the shovel is drawn to its proper position. It
will load and discharge two loads a minute by the force of the cattle.
A
CONCISE history of the Steam Engine, from its first discovery to the present
day, will perhaps be accept able and useful to those who may not have an
opportunity of reading the Encyclopedia, or other rare and expensive
philosophical works, where a fuller account thereof is to be found. It may also
excite the curiosity of ingenious young men to procure those works and read
them; and to acquire a knowledge, which may qualify them to be more useful to
their country.
"The
steam engine was beyond all doubt invented by the Marquis of Worcester during
the reign of Charles II. This nobleman published, in 1663, a small book
entitled A CENTURY OF INVENTIONS; giving some obscure and enigmatical account
of a hundred discoveries or contrivances of his own, which he extols as of great
importance to the public. He appears to have been a person of much knowledge
and great at ingenuity: but his description or accounts of these inventions
seem not so much intended to instruct the public, as to raise wonder; and his
encomiums on their utility and importance are to a great degree extravagant.*
His account, however, of the steam engine, although by no means fit to give us
any distinct notions of its structure and operation, is exact as far as it
goes, agreeing precisely with what we now know of the subject. It is No.68 of
his inventions. His words are as follow: ' This admirable method which I
propose of raising water by the force of fire has no bounds if the vessels be
strong enough: for I have taken a cannon, and having filled it 4ths full of
water, and shut up its muzzle and touch-hole, and exposed it to the fire for 24
hours, it burst with a great explosion. Having afterwards discovered a method
of fortifying vessels internally, and combined them in such a way that they
filled and acted alternately, I have made the water spout in an uninterrupted
stream 40 feet high; and one vessel of rarefied water raised 40 of cold water.
The person who conducted the operation had nothing to do but turn two cocks; so
that on vessel of water being consumed, another begins to force, and then to
fill itself with cold water, and so on in succession.'* It does not appear that
the noble inventor could ever interest the public by these accounts."
* He
was perhaps as capable of invention as any man ever was, Suid we think him
extravagant, only because we (do not understand him. The human mind seems
incapable of believing any thing that it cannot conceive and understand to be
possible, excepting what respects the dogmas of religion, to which we often
yield implicit faith, without inquiring into the possibility or even
probability tbereof. I speak from experience; 10' when it was first asserted
that merchant flour mills could be constructed to attend themselves, so far as
to take the meal from the stones and this wheat from the waggon, and raise them
to the upper stories, spreading the meal to cool, and gathering it by the same
operation into the bolting hopper, to be bolted, etc etc. until the flour was
ready for packing; the projector was answered, " You cannot make water run
up hill, you cannotmake wooden millers." It was thought impossible, and
the inventor to be as wild in his idea', and his assertions as extravagant as
any of the Marquis of Worcester's ,' Century of Inventions," are now
believed to be: but we are now forced to acknowledge, that what he said
concerning the steam engine, was trade, as well as of the telegraphe, the
conversive statue, &C and in proportion as we understand him, and see his
inventions in operation, we will believe, and cease to charge him with having
been extravagant in his encomiums on their importance and utility.I beg leave
to differ with the writer, in his assertion that the Marquis's description of
his steam engine, is not sufficiently clear and explicit, so as to enable an
ingenious workman to discover its principles, construct an engine and put it in
practice.
ÉÉÉÉ.shovel
which scoops it up. B the edge of the shovel, made of sheet-iron, 4 feet wide,
strengthened by a steel plate in front 8 inches wide. R a piece of timber to
strengthen the shovel. Q one of the hind wheels. F one of the handles. G a
treadle. H a chain connecting the treadle to the handle. I one of the iron bars
connecting the shovel to the axle of the fore wheels L.
THE OPERATION.
The
cattle are hitched to the bars I, and the man at the handles guides the point
of the shovel B between the solid and loose earth to scoop up a load, driving a
quantity before the shovel. If the load proves too heavy he puts his foot on
the treadle and raises the point of the shovel B a little, which causes it to
drop part of the load, especially in hollow places; and when the machine
arrives at the place where the load is to be deposited, he throws up the
handles suddenly which drives the shovel into the solid earth, and the force of
the cattle turns the shovel over, bottom up, the bar N to rest on the iron bars
I, and discharges the load. The shovel remains in this position, the bars 0
sliding on the ground, until the machine arrives at the place to take up
another load, when by the rope P the shovel is drawn to its proper position. It
will load and discharge two loads a minute by the force of cattle.
OF CAPTAIN SAVARY'S STEAM ENGINE.
"
CAPTAIN SAVARY, a gentleman of great ingenuity and ardent mind, saw the reality
and practicability of the Marquis of Worcester's project. He knew the great
expansive power of steam, and had discovered the inconceivable rapidity with
which it is reconverted into water by cold; and he then contrived a machine for
raising water, in which both of these properties were employed. He obtained his
patent after having actually erected several machines, of which he gave a
description in a book intitled THE MINER's FRIEND, published in 1696, and in
another work published in 1699. Much about this time Dr. Papin, a Frenchman and
fellow of the Royal Society, invented a method of dissolving bones and other
animal solids in water, by confining them in close vessels, which he called
DIGESTERS, so as to acquire a great degree of heat."
"We
may add, that much about the same time Mr. Amontons contrived a very ingenious
but intricate machine, which he called a fire-wheel. It consisted of a number
of buckets placed in the circumference of a wheel, and communicating with each
other by very intricate circuitous passages. One part of this circumference was
exposed to the heat of a furnace, and another to a stream or cistern of cold
water. The communications were so disposed, that the steam produced in the
buckets on one side of the wheel drove the water into the buckets on the other
side, so that one side of the wheel was always much heavier than the other; and
it must therefore turn round, and may execute some work. The death of the
inventor, and the intricacy of the machine, caused it to be neglected.* Another
member of the Parisian academy of sciences (Mr. Deslandes) also presented to
the academy a project of a steam wheel, where the impulsive force of the vapour
was employed; but it met with no encouragement. The English engineers had by
this time so much improved Savary's first invention, that it supplanted all
others. We have therefore no hesitation in giving the honour of the first and
complete invention to the Marquis of Worcester; and we are not disposed to
refuse Captain Savary's claim to originality as to the construction of the
machine, and even think it probable that his own experiments made him see the
whole independent of the Marquis's account."
Captain
Savary's engine, as improved and simplified by himself, is as follows.
It
consists of a strong copper boiler, properly built up in a furnace; a receiver
in which he formed a vacuum, by expelling the air with steam which was then
condensed; a pipe descending from the bottom of the receiver to the water in
the well; another pipe ascending to the reservoir into which the water is to be
raised; a steam pipe leading from the top of the boiler into the top of the
receiver, in which pipe is a cock, which being turned lets the steam rush into
the receiver, to drive out the air through a valve inserted in the rising pipe;
then a jet of cold water is let out of the rising pipe into the receiver, to
condense the steam and form a 'vacuum, which being done, the pressure of the
atmosphere presses the water in the well up the lower pipe, and fills the
receiver, which is prevented from returning to the well, by the shutting of a
valve fixed in the pipe. The steam cock being again turned, lets the steam
press on the surface of the water in the receiver, and forces it up the rising
pipe into the reservoir; another jet of cold water let into the receiver, forms
a vacuum, and the water rises from the well to fill the receiver again, &c.
It is hardly necessary to mention, that the top of this receiver must always be
within less than ~3 feet of the surface of the water in the well, or else the
pressure of the atmosphere will not force the water up into it. The contrivance
is ingenious.
In
the year 1791 or 1792, I met with a description of the principles and operation
of that curious toy, called the pulse glass. I saw in it principles which I
conceived might be applied to mechanical purposes, for raising water or turning
mills. I set my mind immediately to discover the means of application. After
being engaged in this study, at leisure hours, for 9 years, and having formed a
great variety of plans, of which none appeared sufficiently simple, to he
worthy of experiment, I conceived the idea of a hollow wheel, to be made of
metal, and filled about half fill with spirits of wine, or 'water. After
expelling the air sn as to form a vacuum 'ii the upper part of the wheel, it
must he closed up tight, so as neither to emit air, nor emit steam. There are
no working cocks or valves, or moving parts, excepting the axle on which it is
hung ~d which turns out its gudgeons like those of the water-wheel of a mill.
This wheel being set over a fire, with the flue confined, so as to embrace
about 14th part of its circumference, will turn round with a very low degree of
heat, on the principles of the pulse glass, but it is then weak in power. The
heat of the fire generating steam in the lower and rising quarter of the wheel,
forces the liquid to the descending and upper quarter of the wheel, and it
turns ro'ind slowly, by the weight of the water, being greater in the
descending than in the ascending side of the wheel. I suppose it would produce
no effects worthy of notice, on this principle alone. But when I apply, in
addition thereto, my new principle of confining and retaining the steam, and
increasing the heat, thereby to increase the elastic power of the steam, in a
rapid ratio, and by applying a small slower of cold water to the top of the
wheel, to condense the steam there a little, say 30 degrees, from 272 to 2420
the power of the steam in the lower quarter of the wheel will he 60 pounds to
the inch, and in the upper quarter reduced to 30 pounds; the one being double
the other the greater will overpower the lesser, and drive the water with great
velocity from the lower to the upper quarter of the wheel, and it will move
round rapidly with great power, and perform much work. I constructed a wheel of
lead to work on these principles, which moved slowly, agree ably to my
calculations; I have therefore no doubt, of the operation of the principles.
Considering its great simplicity, having excepting the gudgeons, no working or
wearing parts; that being once filled with spirits of wine, which would require
much less fuel than water, it requires no supply; that 55 no vapour is suffered
to escape the spirits could not diminish in the wheel, I think it the simplest
and perhaps most philosophical steam engine ever conceived. Although it would
he expensive to erect in the first place, it might excel all others, ever yet
constructed. I am however satisfied with what I have already in use; but if I
expected to live 100 years longer, and could spare the money and time, I would
think it worthy of a 1011 experiment. I have specified it, and described
drawings thereof, which I have filed in the patent office, that it may not be
lost.
ÉÉÉÉ.density
of a vacuum being speedily formed, and a piston of a projected machine, which
was to propel a piston by means of air, took the hint and conceived the idea of
forming this vacuum by means of steam, which gave rise to his celebrated engine
that was wrought by the weight of the atmosphere. He constructed an engine
consisting of a large boiler, properly set in a furnace, a little above which
he set a cylinder, nicely bored and polished smooth within, and fixed a piston
air-tight to move up and down therein; the piston was suspended to one end of a
lever or working beam, and the pump rod was suspended at the other end, and was
considerably heavier than the piston so as to draw it up to the top of the
cylinder. The steam being let from the boiler by turning a cock or the like
into the lower end of the cylinder, filled it with steam, which being lighter
than the air drove the air all out at a small valve or clack fixed at the
bottom of the cylinder for that purpose. This done, a jet of cold water was let
into the cylinder, to rise through its bottom and strike against the underside
of the piston, and falling in a spray dispersed over the inside of the cylinder
instantly condensed the steam, forming a vacuum under the piston in the
cylinder; when the pressure of the atmosphere on its upper side, about 15
pounds to the inch, being no longer balanced by air nor steam below, acted as
the power to drive the piston to the bottom, drawing up the pump rod, to make a
stroke. At the instant the engineer saw the piston arrive at the bottom of the
cylinder, he opened the steam pipe to let the steam from the boiler into the
cylinder, to balance the weight of the air on the piston; the superior weight
of the pump rod at the other end of the lever beam, raised the piston to the
top of the cylinder, when a jet of cold water was let in again to condense the
steam, to form a vacuum, produce another stroke, and so on. 'this engine was
offered to the public in 1705, but many difficulties occurred in the execution
which were removed one by one, an4 it was it not until the year 1712 that the
1:3
But
the great defect of this machine, is the prodigious waste of steam, and
consequently of fuel; for the steam at every stroke comes in immediate contact
with the cold surface of the water, and cold top and sides of the cylinder; and
daily experience shows, that a few scattered drops of cold water will condense
a great quantity of steam, almost instantaneously; by some experiments,
frequently repeated, by the writer of this article, it appears, that no less
than 1555 of the whole steam is uselessly condensed in this manner, and not
more than ~1 is employed in allowing the water to descend by its own weight, to
run out of the receiver; and he has reason to think that the portion thus
wasted will be considerably greater if the steam be employed to force the water
out of the receiver to any considerable height."*
Numerous
attempts have been made to diminish this waste, but all to little purpose. Mr.
Blackey has attempted to lessen it, by using two receivers; in the first was
oil, and into this only the steam was admitted; this oil passed to and fro
between the two receivers, and never touched the water except on a small
surface, but this hardly produced a sensible diminution of the waste. This was
done about the year 1700.
OF NEWCOMEN'S ATMOSPHERIC STEAM ENGINE.
MR.
NEWCOMEN, an ingenious blacksmith of Cornwall, a person of some reading, who
was particularly acquainted with the writings and projects of his countryman,
Doctor Hooke, and with the principles and construction of captain Savary's
steam engine, is supposed to have improved on some hints given him by Dr.
Hooke, respecting the himself the writer had taken into consideration, the
rapid ratio of the decrease of the elastic power of the steam as the heat is
diminished, he could have entertained no doubt but that the waste of power is
far greater than he has stated it to be, perhaps not less than nineteen-
ÉÉÉwater
cooling the cylinder, which having to be heated up at every stroke, condenses a
great part of the steam. We have frequently attended to measure the weight of
the steam which filled a very light vessel, that held 12,600 grains of water,
and found it always less than one grain. So that we have no doubt of its being
much more than 10,000 times rarer than water. Desaugulier says, it is 14,000
times rarer than water, and from some experiments to ascertain the water used
at each stroke of the engine, we may safely suppose, that only + of the steam
is employed in allowing the piston to rise, the remaining '~ being employed to
warm the cylinder. The great obstacle to its extensive use, i~ the expense of
fuel; an engine having a cylinder 4 feet diameter working night and day,
consumes about 3400 chaldrons (London) of coals per year, or about 400 bushels
per day.
To
lessen this expense "every one had his particular nostrum for the
construction of his furnace, and some were undoubtedly more successful than
others. But science was not yet sufficiently advanced: it was not till Dr.
Black had made his grand discovery of latent heat, that we could know the
intimate relation between the heat expended in boiling off a quantity of water
and the quantity of steam that it produced."
OF JAMES WATT'S IMPROVEMENTS ON THE STEAM
ENGINE.
ABOUT
the time of the discovery of latent heat by Dr. Black, in 1763, Mr. James Watt,
a man of a truly philosophical mind, eminently conversant in all branches of
natural knowledge, and the pupil and intimate friend of Dr. Black, was amusing
himself with repairing a working model of the steam engine, belonging to the
philosophical apparatus of the university, the thought occurred to him to
attempt the condensation of the steam in a vessel separate from the cylinder.
This
he found to succeed beyond his most sanguine expectations, and proved a great
saving of steam, consequentlyÉÉÉ.
ÉÉÉengine
seemed to give confidence in its efficacy. The most exact and unremitting
attention of the manager was required to the precise moment of opening and
shutting the cocks, as neglect might be ruinous. At last, in 1717, Mr.
Beighton, a very ingenious and well-informed artist, simplified the whole of
the subordinate movements, and brought the machine into the form in which it
has continued without the smallest change, until the present day.
We
now see the great difference between Savary's and Newcomen's engine in respect
of principle. Savary's was really an engine which raised water by the force of
steam; but Newcomen's raises water entirely by the pressure of the atmosphere,
and steam is employed merely as the most expeditious method of producing a
void, into which the atmospherical pressure may impel the first mover of his
machine. The elasticity of the steam is not the first mover.* This engine still
laboured under the great disadvantage of great waste of the steam, occasioned
by the injection ofÉÉ.
This
invention and discovery of Newcomen's, made from the hint given by doctor
Hooke, in 1705, just 100 years ago, was the first step (an enormous stride)
from the simple path of nature Here they lost sight of the true principle
discovered by the Marquis of Worcester, be-fore they had gained sufficient
knowledge thereof, to enable them to apply it to a useful purpose; and
wandering ever since have had faint glimpses of it, but have never returned to
the true path. Had Newcomen constructed a strong boiler, such as used by
Savary, and applied the force of his steam simply to lift the piston, and the
piston to lift the pump-rod to make the stroke, and let his steam escape
uncondensed, lie would have performed at least ireple the work with the same fuel,
with out endangering the bursting of his boiler. But finding his engine, be it
improved, so far to excel Captain Savary's for most purposes; having got clear
of the great difficulties which Savary laboured under, occasioned by his losing
almost all his power after he had generated more than sufficient, had it been
rightly applied ; having established tables and rules for constructing and
proportiolling the engine to the task assigned to it; and finding it extolled
as the greatest discovery ever made in the art, was indeed not to be expected
that any person under such weighty incumbrances could ever return to the true
path. It was only to be expected from one who unincumbered by scientific
shackles, was fret to go as nature guided.
It
may not be here improper to state the actual performance of some of these
engines, as they have been ascertained by experiment.
An
engine having a cylinder of 31 inches in diameter, and making 17 douse strokes
per minute, performs the work of forty horses working night and day (for which
three relays or 120 horses must be kept,) and burns 11,000 pounds of
Staffordshire coal per day.* A cylinder of 19 inches, making 25 strokes of 4
feet each per minute, performs the work of 12 horses working constantly, and
burns 3700 pounds of coals per day.** A cylinder of 24 inches, making 22
strokes of 5 feet, burns 5500 pounds of coals, and is equivalent to the
constant work of 20 horses. And the patentees think themselves authorised by
experience to say in general, that these engines will raise more than 20,000
cubic feet of water 24 feet high for every hundred weight of good pit coal
consumed by them."
*Which
is about 83 pounds, or about 1 bushel of coals to do the work of a horse.
**Which
is about 102 pounds of coals to do the work of horse. Which is 91 pounds of
coals to do the work of a horse.
Mr.
Watt, among his first speculations on the steam engine, made some attempts to
produce an immediate circular motion. One in particular was uncommonly
ingenious. It consisted of a drum turning air-tight within another, with
cavities so disposed that there was a constant and great pressure urging it in
one direction. But no packing of the common kind could preserve it air-tight
with sufficient mobility. He succeeded by immersing it in mercury, or in an
amalgam which remained fluid in the heat of boiling water; but the continual
trituration soon calcined the fluid and rendered it useless. He then tried
Parent's or Dr. Barker's mill, inclosing the arms in a metal drum, which was
immersed in cold water. The steam rushed rapidly along the pipe which was the
axis, and it was hoped that a great reaction would have been exerted at the end
of the arms; but it was almost nothing. The reason seems to be, that the
greatest part of the steam was condensed in the cold arms. It was then tried in
a drum kept boiling hot; but the impulse was now very small in comparison with
the expense of steam. This must be the case."*
ÉÉ.of
fuel; but he was obliged to extract the air from the con denser, by a small
pump, to keep up the vacuum, as all water produces more or less air by boiling.
His next improvement was to obtain a double stroke, up as well as down. To
effect this, he shut up the upper end of the cylinder, passed the piston rod
through a stuffing box made air-tight, and introduced the steam above the
piston to press it down as well as up instead of the atmosphere. The steam
escaped by pipes leading from each end of the cylinder into the condenser, and
shutting the atmosphere totally from the inside of the cylinder proved a
further saving, as the cylinder remained hot, and did not condense the steam.
These are his principal improvements. Many difficulties occurred in the
execution, which his fertile mind surmounted as they occurred. He made great
improvements in the form of furnaces and boilers, and many others in the
subordinate movements, so as to render the machine applicable to most purposes,
far more easily governed, capable of being varied in power, to suit any task
assigned to it, and as regular in its operations as a water-wheel. " In
the engine in its most perfect form, there does not seem to be above -41 part
of the steam wasted, in heating the apparatus, so that it is not possible to
make it ~ part more powerful."*
The
fact is that an engine of this construction, of the same dimensions with a
common engine, making the same number of strokes of the same extent, does not
consume above 45- part of the fuel that is consumed by the best engines of the
common form.
It
is evident that when the writer said, '~ that it is not possible to make it
one-fourth more powerful," he had no knowledge of the great saving of fuel
and increase of power, that would he the result of onfluing the steam, and
increasing the heat and elasticity of the steam; or of applying this great
elastic power, to propel the piston, by which the power may he increased
tenfold, and the fuel be reduced to one-third to perform equal work; yet it
seems that this same writer gives the set of experiments which ascertains the
Caistence Of the principleÉ..
Steam
having no weight we cannot expect it to re-act with much force, by issuing from
the rotary tube. This is the reason it produces so little power in this
application. I therefore have contrived a steam engine wherein the elastic
power of the steam is to force oil or quicksilver (if any means can be
discovered to keep it fluid) through the rotary tube; when the engine will work
with great power, and produce an immediate rotary motion. I have also contrived
two forms of wheels, not before mentioned, making five different forms; all of
which I have specified and explained by drawings, &c. according to law, as
different modes in which I contemplate using my principle, of confining and
retaining the steam and increasing the heat, to increase the elastic power of
steam, for the purpose of saving fuel, and lessening the expense of
constructing engines, none of which 'will ever be worth notice without said
principle. But on mature deliberation I have reason to conclude that none of
them will ever excel the cylinder and piston, so far as to be worthy of my time
and attention to put them in operation.
It
is evident from this account that Mr. Watt, in these experiments, has used weak
steam, and placed dependence on the use of a condenser. Had he in his experiment
with Dr. Barker's mill, lessened the apertures by which the steam issued, 50 as
to confine the steam until the power in the boiler was equal to 100 pounds to
the inch, lie would have been astonished, to see it revolve about 1000 times in
a minute, supposing the rotary tube to have been 3 feet in length. I have tried
the same experitment, but without the least hope of success, on any other
principle than by confining the steam to increase its elasticity, to a great
degree My rotary tube was 3 feet long, the elastic power of the steam about 56
pound to the inch. It revolved with a velocity of about 700 or 1000 times per
minute. The apertures by which the steam issued, about 2-hathes of an inch
diameter. It exerted more than the power of two men, and would answer to turn,
lathes, grindstones, &C where fuel is very cheap. I have specified and
explained it in die patent office.
I
here close my extracts from the Encyclopedia, as my limits will not admit of
doing justice to the merits of the different inventors and improvers of steam
engines ; and I must refer the readers to the work itself, where they may
expect to be both pleased and edified, if they wish to understand fully, the
most philosophical and useful machine ever invented.
OF LATE INVENTIONS OR IMPROVEMENTS ON STEAM
ENGINES.
A man's useful inventions, subject him to
insult, robbery, and abuse.
FRANKLIN.
THE
truth of the above observation is daily verified. No man ever made a useful
discovery, invention, or improvement, to which he claimed exclusive right,
under the protecting laws of his country and was permitted to enjoy such right
peaceably. He may expect to be attacked by a host of claimants, who to support
their claims, load the inventor with heavy abuse, and he is obliged at great
expense to defend himself.
The
author when a boy, was led to the study of the possibility of moving land
carriages without animal force, which he viewed as a very desirable object. He
had heard of various attempts having been made, by means of cranks, wheels,
pinions, springs, wind, &c. all of which appeared to him as too futile to
be worthy of attention, from the want of original power. Instances had
occurred, of the great explosions made by a small quantity of water confined in
the breech of a gun-barrel, exposed to a smith's fire. Ilere he saw original
power, which he conceived to be unlimited, but had formed no idea of the means
of its application, until he met with a description of an atmospheric steam
engine.
He
was astonished to find that the steam, was not applied as the prime mover, but
only as the means to form a vacuum, to apply the weight of the atmosphere. This
he conceived to be a great error, and the more he investigated the subject, the
more he was confirmed in this opinion; for it appeared clear to him, that the
elastic power of the steam rose in some rapid ratio compared with the increase
of heat, otherwise the power could not he augmented in so short a time, to a
degree sufficient to make explosions equal to gun-powder. He conceived that
double heat in the water did produce 8, 10, 16, or 32 times the power of steam,
and perhaps more. These ideas existed some years before he conceived the plan
of constructing small engines, to be moved by this irresistible power, to work
with steam equal in power to 10 atmospheres, that would be capable of moving
land carriages with heavy burdens. Not satisfied with the cylinder and piston,
because it did not produce an immediate circular motion, he endeavored to
discover means of applying the expansive power of steam to a wheel, which he
matured in 1784. This wheel is now described in the patent office, and called
his Circular Steam Engine, No.2. He was then confident that he could propel, by
means of steam, land carriages and boats to great advantage: but as the expense
was very considerable, in the first instance, he explained the principles to
every person with whom he conversed on the subject, in order to induce some one
or other to join him in the enterprise. Having matured his improvements on
merchant flour mills, he applied to the state legislatures of Pennsylvania and
Maryland for exclusive rights, and included in this application the right of
propelling land carriages, by the power of steam, and the pressure of the
atmosphere. Boats were not included; supposing the exclusive right in those
states was not worth obtaining. Pennsylvania granted for the mill improvements
only, Maryland for both mill improvements and land crriages-. While waiting on
the legislature of Maryland, hewas introduced to a gentleman, (Mr. Masters) an old
sea-captain, who had obtained the name of a projector, by having contrived a
machine to draw trees up by the roots, which was found not to answer well in
this country. This gentleman was possessed of a philosophical and mechanical
genius, and was extremely anxious to be acquainted with the principles of the
engine, that was to propel land carriages and boats. They. were made known to ,
and he expressed his approbation by saying, that a large engine on those
principles would be useful if applied on board a ship crossing the Atlantic, to
increase her despatch, in cases of emergency, by being used in calms, and
during head winds. He said he was going to England in a short time, and asked
permission of the inventor to explain the principles of his engine to people
there Many other instances occurred, by which the principles of the invention
might have been early communicated to English engineers. Drawings and
explanations nations were sent to them, but it seems they were satisfied that
they had arrived at the utmost possible state of perfection, and were therefore
not easily moved.
Although
the inventor had obtained a patent of the state of Maryland, before the United
States' government was authorized to grant patents, he was so engaged with the
introduction of his mill improvements, that he could not prosecute his
inventions on steam engines, further than filing drawings and specifications of
the principles in the patent office in 1792, and trying some experiments which
confirmed him in his principles. In the year 1801 he commenced the execution of
an engine, and in the winter of 1802, got it in full operation. Its performance
excited considerable attention and curiosity.
On
the day of Doctor Coxe of Philadelphia called on him with a letter from John
Stevens, Esq. of Hoboken, New-Jersey, dated Feb. 7, 1804, propounding a number
of questions, respecting the principles and construction of the engine, which
he had heard was so powerful as to do the great work that had been stated in
newspapers which had fallen into Mr. Stevens's hands. After having received
assurances, that Mr. Stevens intended no interference with the inventor, he
proceeded to answer all his questions, and to explain the principles and
construction of his engine, as fully and freely as he had done to any other
person; all which Dr. Coxe thinks he communicated in his answer to Mr. Stevens,
as far as his memory and short pencil notes enabled him to do. Some time after
this Dr. Coxe called again with another letter from the said Stevens, dated
February 16, 1803, propounding another list of questions, which, after similar
assurances being given, that no interference was intended, nor need to be
feared, were answered, and the whole of the principles explained. Dr. Coxe
called at two other different times on the same subject, and the inventor is
free to say, that to no gentleman whatever, (excepting only Mr. Charles Taylor,
steam engineer, and Mr. Robert Patterson, professor of mathematics in the
university of Pennsylvania) has he explained the principles of his invention
with more care and exactness than he did to Dr. Coxe. This he was the better
able to do, having before that time committed the whole thereof to writing,
from which he has since compiled his new work on steam engines. In the month of
January, 1805, he laid the following printed circular letter before the members
of congress:
THE
subscriber with diffidence presumes to lay before the honourable Senators and
Representatives in Congress, individually, (hoping it may be well received) the
following concise description of the principles of Steam Engines.
The
present English steam engine, so much celebrated, consisted, in it first state,
of a boiler to generate the steam; to which was connected a cylinder, open at
top, in which a piston moved up and down, which was attached to a working beam,
hung on its centre, the other end of which was connected to a pump. The steam
was let into the cylinder below the piston, to balance the atmosphere; and the
weight of the pump rod, at the opposite end of the beam, raised the piston up
to the top of the cylinder; the steam was then shut off; and a jet of cold
water let into the cylinder, to condense the steam, and form a vacuum under the
piston in the cylinder.; and then the weight of the air on the top of the cylinder,
which is l5lbs. to every square inch of its area, being no longer balanced, was
the power which drove down the piston and drew up the pump rod to make a
stroke. If they could have made a perfect vacuum by these means, the power of
the engine would have been 1 15lbs. to every inch area of the piston; but it
was found not to exceed 81lbs. and required large quantities of fuel, great
part of the steam being lost in heating up the cylinder at every stroke, which
was cooled by the jet of cold water. This is called the single-stroke engine.
The
celebrated James Watt improved this engine, by making his steam of power equal
to the weight of the atmosphere, and letting it in at the top of the cylinder,
to supply the place of the atmosphere to push down the piston, while the steam
was condensed below, and also at the bottom, while condensation was going on
above, making a double stroke; and to avoid the loss occasioned by the jet
cooling the cylinder, he led the steam off from each end of the cylinder into a
seperate vessel, into which he let the jet of cold water to condense the steam.
He found by these means he could make a more perfect vacuum, and computed the
power of his engine at between 11 to l3lbs. to the inch. The expense of fuel
was greatly less'ned.
This
is Watt's double-stroke steam engine, so celebrated and very justly deemed the
greatest of all human inventions. Although it be so limited in its power, to
double the power they make an engine of double capacity, and it requires double
fuel, This engine labours under the following disadvantages:
There
is a continual accumulation of air in the condenser not even suggested that
this principle might be applied to any use,) which ratio, continued from 212 to
424 degrees double heat in the water, gives 128 times the power of steam; and
it is absurd to suppose that it would require 128 times the fuel to be expended
in an equal time to produce double heat in the water; and if not, then this new
principle will require less fuel to produce equal power.
To
apply this wonderful principle, I construct my boilers of circular cylindric
forms of small diameters, the best possible form to contain a great elastic
power; and to enlarge their capacity, I extend their length or increase their
number, which also gives a large surface for the fire to act on, making them
sufficiendy strong to contain steam of elastic power equal to 15001bs. to the
inch area of the piston, which would give my engine 100 times the greatest
possible power of the English principle: but at the same time arranging the
work so that 50lbs. to the inch power will be sufficient in ordinary cases, and
so that we cannot without considerable trouble and difficulty, ever raise the
powers to exceed 150lbs. to the inch in the most extraordinary case; greater
power we will never want, which makes the engine perfectly safe from explosion,
as it will bear from 10 to 30 times the power that we shall ever have need of
using, and be from 5 to 10 times as powerful as Watt's engine. I have an engine
in operation in the most simple form without a condenser, which is capable of
performing three times the work with equal fuel, compared with the English
engine; and succeeds according to theory, working with steam, generally equal
in power from 50 to 1001bs. to the inch; doubling the fuel appears to produce
about 16 times the power and effect. Its great power and simple structure fits
it for propelling boats up the Mississippi, and carriages on turnpike roads,
two of the most difficult applications; therefore will apply to all others as a
powerful agent.
I
have conceived further, and still greater improvements, which I wish to put in
operation.
ÉÉ..generated
by boiling the water, which would destroy the vacuum in a short time, and stop
the engine; therefore an air pump is constantly at work to extract it. Also a
continual accumulation of sediment, which adheres to the bottom of the boiler,
forming a non-conductor of heat, causing the boiler to burn out; they are
obliged to stop once or twice a month, let all cool, and open the boiler to go
inside to scrape away the sediment.
The
boilers are constructed to bear little or no power of steam, their principle
being to make the steam inside the boiler equal to the atmosphere outside; and
if ever the safety-valve is overloaded, or a double weight laid on by accident,
and the steam does not get vent, the boiler explodes; and if ever the steam in
the boiler is suddenly condensed by a dash of cold water on its top, &c. it
collapses, being pressed in by the weight of the atmosphere. The principles of
the engine are dangerous, ever liable to these accidents, and it was generally
believed that nothing could be gained by increasing the power of the steam to
exceed atmospheric power.
My
ideas of the application of the power of steam were very different at the
first. I conceived the power to be irresistible; that the power increased in
some very rapid ratio, as we increased the heat in the water; otherwise it
could not rise to such a pitch in so short a time, as to make the terrible
explosions which I had known of: I supposed that doable heat in the water,
would give eight, or sixteen, or perhaps thirty-two times the power of steam.
On these principles I conceived that I could obtain any power I pleased, simply
by confining the steam and increasing the heat, and perhaps with less fuel, and
a much smaller engine. After I had commenced the construction of an engine on
these new principles, I was informed that some curious and philosophic
gentlemen had made a set of accurate experiments, the result of which was that
every addition of thirty degrees of heat to the water by Fahrenheit's
thermometer, be the temperature what it say, doubles the bulk and elastic power
of steam, (but hadÉÉ..
ÉÉÉÉdregs
pass off at the other end in a continual stream. And in which, principles are
adopted to suppress the watery vapour until the spiritous vapour may rise with
a very rapid process, to obtain purer spirits at the first distillation.
The
principles of this invention may be conceived, when we consider the common
process of distillation, which I suppose to be as follows, viz. The pressure of
the atmosphere which is equal to l5lbs. to every square inch surface of the
beer in the still, suppresses the watery vapour until the beer is heated to 212
degrees of Fahrenheit's thermometer, or boiling heat; but the spirits being
more volatile, its vapour is about double as powerful, and will rise under that
pressure at 170 degrees of heat, 42 degrees below the boiling point of water:
now, while the heat is kept between those two points, purer spirits are
obtained; but the process is too slow, and the distiller to increase it, makes
his still boil, which raises large quantities of watery with the spiritous
vapour. Now it appears evident, that if we sue the path pointed out by nature,
we may, by increasing the pressure, suppress the watery vapour until the
spirits rise rapidly, and use less fuel; but this is much more difficult to
explain. Any further explanation required, I am willing to give.
OLIVER EVANS.
The
foregoing letter was sent by Dr. Mitchill, a senator from the state of
New-York, to his friend Dr. Miller, one of the editors of a periodical work,
entitled the Medical Repository, to be published therein. John Stevens, Esq. of
Hoboken, (New-Jersey) having seen and read it, thought proper to make the
following remarks, which were published in the same number of the Repository
with the letter.
1st.
The inexhaustible steam engine, so called, because it is arranged on such
principles that the water in the boiler will not be exhausted by boiling and
working the engine; by which means I evade the accumulation of sediment from
the water, as it forms a non-conductor of heat on the bottom of the boiler,
which will cause it to last 10 times as long. I also evade the accumulation of
air to interrupt the vacuum, by which means the vacuum will become more
perfect, and the engine have more power, and require less fuel. The principles
on which this is done may be easily conceived, if we suppose a still with its
condenser so elevated that the worm, after it leaves the condenser, may be
turned to lead the spirits back into the still; this still may in theory be
boiled for ever, without being exhausted. Thus, after the steam has passed
through my engine, it is condensed into water, and returns into the boiler
again, and no sediment or air can accumulate from water distilled many times
over.
2nd.
The volcanic steam engine, in which I attempt to use the principles of the
natural volcano, where the furnace and boiler are in one, and where the fire
burns without the aid of the atmospheric air to kindle it; but until I shall
discover a fuel which will so burn, I use a forcing air pump to kindle the
fire. In this engine the boiler and furnace are united, the water round the
fire and the flue of the furnace is made to discharge immediately into the
water at the bottom of the boiler, and bubble up through it, communicating all
the heat of the fire to the water to generate steam; and all the elastic fluid
generated by the combustion of the fuel, which I must suppose will be expanded
to at least 2000 times the bulk of the fuel, unites with the steam to work the
engine, by which means not more than one-fourth part of the fuel will be
required, which fits this engine for boats or carriages better than the other.
3d.
The perpetual still, arranged upon such principles, that the beer is received
at one end, to pass slowly on to the other(r; during which time the sprit is
extracted ,and the projected improvements, and I shall not only listen to you,
but thank you into the bargain. Believe me to be, dear sir, with great esteem
and regard, yours, &c.
JOHN STEVENS.
A
description of his still follows, explained by a drawing, which I cannot give
for want of the plate.
NEW-YORK,
JANUARY 12th, 1805.
DEAR
SIR,
I
AM this moment favoured, by Dr. Miller, with Mr. Evans's project for the
improvement of steam engines. He begins with a short history of this noble
machine, but has (I will not say through design) omitted mentioning the first
attempts made by Captain Savary, in which this very principle of working a
steam engine, with steam at a high temperature, and with great elasticity, was
resorted to, but without success, although he used boilers, strengthened with
radiating bars and bolts within, and strongly hooped without. Here, then, we
find the Principe of using strong steam, at a high temperature, is actually as
old as the invention of the steam engine itself. Mr. Evans, then, can surely
have no well-grounded pretensions to a claim of invention with respect to this
principle. That the elasticity of steam is increased by an increment of
temperature, is surely no novel discovery. But that this increment should bear
a very small proportion to the quantity of heat required for the conversion of
water into steam, was a natural and obvious deduction from the important
discoveries of Dr. Black respecting latent heat. These discoveries you have
yourself, no doubt, heard the doctor detail in his lectures some twenty years
ago; and Mr. Belancour's experiments, instituted for the express purpose of
ascertaining the ratio of increment of the elasticity of steam, at different
temperatures, were made in 1790. Experiments, for the like purpose, were also
made by the editors of the Encyclopedia Britannica, and pubÉÉ..
Remarks
on Mr. Evans's project, and an account of other improvements in steam engines,
by John Stevens, Esq. of Hoboken: communicated in the following letters to Dr.
Mitchill.
NEW-YORK,
JANUARY 9th, 1805.
DEAR
SIR,
You
favour of the 6th instant I have this moment received. Among other projects of
Mr. Evans's, I find you enumerate improvements in distillation. Here Mr. Evans
and myself are likely to interfere. The idea of distilling with steam is not
new. Count Rumford has suggested its practibility in one of his essays. You
must observe that Mr. Evans and myself work the steam engine without any
condensing apparatus. This steam then, after its discharge from the cylinder,
without any diminution of temperature, may be applied to the purpose of
distillation. This application of steam naturally suggested itself to me when I
first made my experiments on working a steam engine with steam at a high
temperature. I have accordingly invented a still adapted to the purpose, simple
and cheap in its construction, and calculated to produce spirit of a much
better quality than can be obtained in the ordinary way of distilling. A
description of my contrivance you will find inclosed; and as it may, in case of
interference, prove of use to me, I wish you to preserve this letter and that
description, noting thereon the date of its reception.
Of
Mr. Evans's volcanic engine, I lately received a description from Dr. Coxe, of
Philadelphia, from which, I must confess, I did not form the most exalted
opinion of Mr. Evans's project. From the many difficulties that presented
themselves, it really appeared to me he was in pursuit of an ÉÉ..
You
say you started a doubt respecting his supposed improvement in distilling. But
although he would not listen to it, the doubt exists as strong as ever." Now,
my dear sir, I intreat you to take the same liberty respecting my ÉÉÉ
ÉÉÉ..years
ago, long before I had heard any thing of Mr. Evans, it occurred to me that a
condenser might be so constructed, as that by exposing a large surface within a
small compass, the steam might be so nearly condensed, as to ~ender a jet of
cold water unnecessary; but, upon trial, I must candidly confess, it did not
answer equal to my expectations. The reason is obvious: the heat could not be
conveyed through the metal with sufficient rapidity, so that the temperature
within the condenser should be sufficiently low to condense all the steam.
[Here
Mr. Stevens has shown that he was not able to comprehend the principles and
construction of this engine; he will surely never claim it hereafter: but if he
had seen ray specifications and drawings, then the application would have been
obvious from the discoveries perhaps, of Newcomen or Watt.
1.
" The volcanic steam engine." But till he shall have discovered a
fuel which will burn without the aid of atmospheric air, I shall desist from
saying any thing about his intended application of this project, to propelling
boats and wheel carriages
[He
means, I suppose, until he sees it in operation, then the application will be
obvious to any one from the burning and explosions of volcanoes.
ÉÉ..ad.
" The perpetual still" Here, if I understand Mr. Evans, he assumes a
very erroneous principle. He concludes that spirits will rise more readily than
water, in proportion as the pressure is increased. But the very ingenious
experiments of Mr. Dalton have proved incontrovertibly, " that the
variation of the force of vapour from all liquids is the same for the same
variation of temperature." Thus the force of the vapour of spirit of wine
at 175 degrees is equal to 15lbs. and the force of vapour of water at 212
degrees is equal to l5lbs.-increase the temperature of both degrees, and the
elastic force of each will be increased equally, viz. to about 261bs. on the
square inch. By some experiments established therein a dozen years ago. The
application of this very important law of increment, developed by these
gentlemen, to the improvement of the steam engine, was obvious; the great
desideratum was to construct a boiler sufficiently strong to withstand a very
great pressure of steam.
[Has
Doctor Black, Belancour, the editors of the Encyclopedia Britannica, (or even
John Stevens, Esq.) ever pointed out the means by which these principles could
be advantageously applied to the improvement of steam engines, or did they even
suggest such an idea
To
apply this wonderful principle," says Mr. Evans, " I construct my
boilers of circular cylindrical forms, of small diameters, the best possible
form to contain a great elastic power; and to enlarge their capacity, I extend
their length, or increase their number." Here Mr. Evans, for the first
time that I have heard of; assumes to himself a principle, for which I have
obtained a patent near two years ago For I would ask, whether his boilers
before, or even since, have been constructed upon the principle above stated?
The boiler he used at the time my patent was obtained, was a metal cylinder of
20 inches diameter, and 20 feet long surrounded by an exterior one of wood. His
present boiler is a like cylinder placed in brick work. The only difference
between them is, that in the former the fire was made within the cylinder; in
the latter it is made to surround i~ He has made no attempt to diminish the
diameter of his cylinder, or to increase the number of cylinders. The latter,
indeed, he could not do without a manifest interference with my patent. Of
this, I doubt not, Mr. Evans himself would be sensible, where he to peruse my
specification filed in the patent office.
But,
it seems, Mr. Evans has " conceived further, and still greater
improvements, which he wishes to put in operation.
1st.
" The inexhaustible steam engine." I have nothing to say about this
sociable project other than that many
All
experimenters agree, that the same law governs both, viz. that within a certain
range every addition of about 30 degrees to the temperature, doubles the
elasticity. In the above scale, the temperature of the spirits is kept 7
degrees below that of the water. When water is 212, and spirits 205 degrees,
the difference is 15lbs. to the inch, and every addition of 30 degrees doubles
the power of both, and doubles the difference; three steps brings the
difference to 60 lbs. when the spirits will rise with great rapidity, and the
watery vapour be totally suppressed. It is wondrous that this was not obvious
to Mr. Stevens, from the discoveries of Belancour and Dalton, that he might
have claimed "the application of it on certain principles, to the
improvement of his notable still."]
While
on the subject of distillation-Can you not suggest to me some varnish or
cement, that will resist the action of alcohol, which I may substitute in the
place of metal for lining my wooden alembics? But spirits are preserved for any
length of time in wooden vessels. ~ Would wood be affected by spirits at a
temperature of 100 to 150 degrees? I am inclined to think that at the low
temperature of the wash in my still, it may not be necessary to defend the wood
from the action of the spirit. I shall at least make a trial.
Mr.
Evans, proceeding on the calculations given in the Encyclopedia and by Count
Rumford, has been led into an error as well as myself, in estimating the
increments of the force of steam with given increments of temperature. It is
laid down by these authors, that for every increase of 30 degrees of temperature
the elasticity of steam is doubled. But Mr. Dalton has proved that the ratio is
not equable and constant, but is a gradually diminishing one.
|
Temperature |
Force of Vapour |
Temperature |
Force of vapour |
|
9.46 |
160 |
19 |
340 |
|
|
`190 |
34.99 |
370 |
|
|
220 |
58.21 |
400 |
|
|
250 |
88.75 |
430 |
But
Mr. Dalton has proved, from a series of very accurate experiments on the
elasticity or force of sulphuric ether, at different temperatures, from 32 to
212 degrees, that the increments of force are in a direct ratio to the
increments of force of watery vapour from 142 to 322 degrees. The boiling point
of ether in the open air being 102, that of water 212 degrees.
It
is presumable, therefore, that spirit vapour is governed by the same law of
increment, and that Mr. Achard committed some error.
[Had
I permitted Mr. Stevens to have palmed such an error or misrepresentation on
the public, to remain as an impediment to improvements, and especially to my
proposed improvement on distillation, I would have been guilty of a neglect of
duty. He says that the force of vapour at 175 degrees is equal to 15lbs. then
he should have stated it thus:
|
Temp of watery vapour |
Temp of spiritous vapour |
In mer |
Elasticity or force of both |
|
209 |
1730 |
28.1 |
36 |
|
189 |
154.6 |
18.5 |
34.4 |
|
168 |
134.4 |
11.05 |
33.6 |
É.experience,
in this bewitching department of experiments and inventions, ought to have
taught me long ago, the truth and accuracy of Mr. Evans's calculation. Mr.
Evans laments that he has already risqued 2000 dollars. Alas! I have risqued
more than ten times that amount, and although I have been more than twenty
years hard at work, I have as yet derived not one shilling advantage from all
my various schemes and projects. If, therefore, now that I think I see some
prospect of indemnification, I should discover some degree of solicitude to
secure the property of an invention, no one, I 'trust, will blame me.
It
may not be amiss to mention, that steam discharged from the cylinder, may be
applied to working one of Watt and Bolton's engines; and I think it probable
that it would not require more fuel than if worked in the common way. In this
case, the whole of the work performed by my engine would be saved.
[I
recollect perfectly well having explained this to Dr. Coxe, as I did to others,
saying, that all the power which I yet had, was so much over and above the
power of Bolton and Watt's engine, that the steam after it left my engine would
work one of theirs; and that I could add their power to my engine, by the use
of a condenser. Mr. Stevens has not conceived this simple mode, but took up the
idea of an additional engine. Indeed, Mr. Stevens, this circumstance added to
all the rest, gives the whole a dark appearance; and your endeavours to impress
the public mind with an unfavourable opinion of my improvements, and that I
have assumed to myself some of your inventions, is both illiberal and injurious
to a great degree.]
Mr.
Evans tells us, " that the great power and simple structure of his engine,
fits it for propelling boats up the Mississippi, and carriages on turnpike
roads; two of the. most difficult applications." Difficult indeed it must
prove, should he attempt to effect either of these purposes with his unwieldy
boiler of 20 feet in length and 3 or 4 feet diameter equal to l30bs. on the
square inch. This we find is very far short of Mr. Evans's extravagant calculation,
that 424 degrees gives steam 128 times as strong as steam at the temperature of
212 degrees. From my experiments detailed hereafter, it will appear that this
calculation of Mr. Dalton's is too low; that 424 degrees would give steam equal
to 450 in.
[Continue
this scale of the diminution of the ratio, and the increase of elasticity by
the addition of heat will entirely cease before the elasticity would be
sufficient to burst one of my boilers; so that Mr. Stevens removes all danger
on that score: but I fear that neither Dalton nor him are right. They have,
however, left me a good power; 1301bs. to the inch is quite sufficient.]
Mr.
Evans exaggerates enormously the strength of his boiler, when he estimates it
capable of sustaining a pressure of 15001bs. on each square inch. Count Rumford
has ascertained, by actual experiment, that a bar of wrought iron, an inch
square, will require about 63000 bs. to fracture it. Mr. Evans's boiler is
composed of wrought iron a quarter of an inch thick, and as it is 20 inches
diameter, or about 60 inches in circumference, 60 multiplied by 1500 is equal
to 90.000 lbs. pressure on each inch of the circumference of his boiler. To
withstand this pressure, it ought to be an inch and a half thick instead of a
quarter. Contrast this with the tubes of which my boiler is composed of an inch
diameter, giving about 3 inches in circumference, 3 multiplied by 1500 is equal
to 4500 1bs. which would require a thickness of only one-fourteenth of an inch
of wrought iron.
[Here
Mr. Stevens has magnified, by his calculations, 15001bs. to the inch
circumference of my boiler to 90,OOOlbs. and then proceeds on his error to find
the thickness of iron necessary to bear it. I advise him to read the rules,
with their demonstrations, which I have laid down.]
Mr.
Evans considers his inventions, although of the utmost importance, as a bad
speculation. in my own sad experimentsconstructed a rotary engine, on the axis
of which revolved a wheel at the stern of the boat like a wind-mill or
smoke-jack. It was impossible to make a more simple application of the power.
After repeated trials, however, I found it Impracticable to preserve a
sufficient degree of tightness in the packing, &c. The yellow fever came on
and interrupted my further progress The next winter I was employed in
constructing another rotary engine on a new plan; but this, on trial, proved no
better than the first. Thus I lost a whole year, and was compelled,
reluctantly, to have recourse to Watt and Bolton's engine. I set immediately to
work, and some time in May last had my machinery all on board a boat. My
cylinder is 4~ inches in the bore, with a 9 inch stroke. The complex machinery
for opening and shutting the valves of Watt and Bolton's engine I have reduced
to a single movement. The lever beam I have dispensed with altogether, as also
with the condensing apparatus and air-pump.
[Here
Mr. Stevens expressly states, that he lost a whole year after he had obtained
his patent, in pursuit of projects which proved futile, and that he was compelled,
reluctantly, to have recourse to Watt and Bolton's engine. Why did he not speak
truly, and say Evans's engine .~ for it is not Watt and Bolton that he follows,
but he treads in my steps exactly. I had in use during two years before that
time all the improvements he had recourse to. The heavy lever beam I had
dispensed with altogether, as well as the condenser and air-pump, and used a
small forcing pump to supply my boiler. The principle of the great elastic
power of steam, discovered by the Marquis of Worcester, (but which had been
abandoned for one hundred years, as unmanageable) I had applied to propel a
piston in a cylinder similar in its construction and operation to Watt and
Bolton's; producing an engine ten times as powerful, expending only one-third
the fuel to (10 equal work, and costing only half the price, compared to Watt
and Bolton's. Mr. Stevens has been reluctantly compelled to follow me, by
adopting all my improvements.]
.
It is plain to be seen, that, to perform these very arduous exploits, Mr. Evans
does not mean to employ his own boilers, but to avail himself of the principle
he has so dexterously assumed to himself, viz. to increase the number of his
cylinders. To place this matter in a striking point of view, I will give yon
the dimensions of a boiler I pro-pose putting on board of a vessel to ply as a
passage boat betwixt this place and Albany. Length of the boiler, 6 feet3
breadth, 4 feet; depth, 2 feet. A boiler of these dimensions will expose, in
the most advantageous manner, upwards of 400 feet of surface to the action of
the fire. To expose an equal surface with a boiler on Mr. Evans's plan, would
require it to be upwards of 80 feet long; but were it twice that length, it
would not give an equal quantity of steam, as it would be impracticable to
apply heat to it advantageously.
Pardon
the great length to which this letter is protracted:
the
objects I conceive myself on the point of accomplishing are of immense
importance. You have sent forward Mr. Evans's paper to be inserted in the Medical
Repository. This has a wide circulation, not only in the United States, but
throughout all Europe. I therefore think, that in justice to myself and the
world, I should have an opportunity of asserting and maintaining what I
conceive to be my right. I should wish, therefore that you would forward this
and my former letter, with a certified copy of my specification, filed in the
patent office, without delay, so that 1 may be able to insert extracts
therefrom, in the same number of the Medical Repository with Mr. Evans's paper.
I am, my dear sir, with the sincerest regard, yours, &c.
JOHN
STEVENS.
It
may not be amiss to go into a short detail of the progress I have made since
obtaining the patent. My object was, in the first instance, to construct an engine,
adapted more immediately to the purpose of propelling a boat. This was an error
which occasioned the loss of the first season.
My
boiler was on a similar construction with the ono described in my
specification. It was 2 feet long, 15 inches wide, and 10 or 12 inches high,
and consisted of 81 tubes, 2 feet long, and 1 inch diameter. As my boat was
nearly 25 feet long, and 5 feet wide, I was not able, with safety, to raise a
chimney of more than 3 or 4 feet high. The consequence was, I was unable to establish
a sufficient draft between the interstices of the tubes, so as to support a
brisk fire; and the power of the engine was, of course, too feeble to give much
motion to the boat. I then altered the furnace ~o as to allow room between the
tubes and the brick work for a draft. This was applying the heat of the fire to
a great disadvantage; but I could do no better. Under these unfavourable
circumstances, however, I made another trial, and gave to the boat a velocity
of about four miles an hour. After having made repeated trials with her, my son
undertook to cross over from Hoboken to New-York, when, unfortunately, as she
had nearly reached the wharf, the steam pipe gave way, having been put together
with soft solder. This threw the crew into some confusion, and by dashing a
pail of water suddenly on the boiler, the immediate contraction of the metal
cracked a number of the tubes, and thus put an end to all further experiments
with this boiler. To avoid a similar accident, I set about constructing a boiler
on another plan. A single plate of brass was placed horizontally, and tubes
were screwed into the under side in a vertical direction. It was rate in the
fall before we could bring our engine into operation again; but for want of
sufficient draft, its performance was not much more powerful than before. It
was kept going, occasionally, for a fortnight or three weeks, the boat making
excursions of two or three miles up and down the river; and, finally, on the
approach of winter, the machinery was taken out of the boat. I will must
mention, that in the spring, previously to putting it aboard the boat, the
engine was set agoing in the shop. At first, a stove pipe was carried out of
one of the windows; but with all our endeavours, though the boiler was perfectly
right, we could not raise the safety valve loaded with about 50lbs. to the
square inch. The flue was then carried out above the roof, and in a few minutes
a few shavings would set the engine agoing. As I was impatient to try its
performance in the boat, I did not apply it to any sort of work, so that I made
no estimate of its power to ascertain how much work it would perform with a
given quantity of fuel. When on board the boat we repeatedly stopped the engine
till the steam would raise the safety valve; when, for a short distance, the
boat would go at the rate of not less than seven or eight miles an hour.
I
am at present employed in constructing a boiler on a different plan from the
last, and which, I expect, will turn out a great improvement on it. And as it
will be much larger, and placed in a building with a lofty chimney, I expect to
be able to work with a load on the safety valve of l00lbs. or perhaps 2001bs.
to the square inch. And as I purpose. pose putting up a pair of mill-stones, I
shall also be able to determine the quantity of work performed with a given
quantity of fuel.*
Should
this, on trial, as I feel fully confident it will, answer my expectations, I
shall immediately set about one on a still larger scale, to be placed on board
a vessel to ply as a passage boat between this city and Albany.
[Mr.
Stevens states that his next boiler will be much larger. His inch tubes will,
no doubt, swell to cylinders of
That
the Saving of fuel must be very great indeed there cannot be a doubt 0. Evans
States that with a 102(1 of 281bs. to the square inch, three times the work is
performed with an equal quantity of fuel. What then 'nay we expect when the
elasticity of the Steam equals lOOlbs. or perhaps 2OOlbs. on the square inch.
The experiments of Dr. Black and others prove, that when water is converted
into Steam, 600 or 900 deg. of heat are absorbed. Now, an addition of less than
400 deg. would bring this steam to the heat of boiling oil, its elasticity
would then (according to my experiments) be equal to 40 atmospheres, or 60Olbs.
on the square inch. Thus then, if 900 degrees equal one atmosphere, 1300
degrees equal 40 atmospheres; but to raise the temperature of steam in the
above proportion Cannot require any thing like 40 times the fuel.
The
area of a circle of three-eighths of an inch diameter is very nearly one-ninth
of a square inch. Thus then, 12+ lbs. the average of weights raised by the
explosions, multiplied by 9, gives 650lbs on the square inch for the elasticity
of the steam at rise temperature of boiling oil, which is usually estimated at
600 degrees of Fahrenheit's thermometer. This is an elasticity considerably
greater than the result which Mr. Dalton's principles of calculation would
afford, but much less than the calculations of Mr. Achard and the editors of
the Encyclopedia Britannica would make it. By the experiments of these
gentlemen, it appears that from 150 to 280 degrees (which was as far as their
experiments extended) an addition of one inch of mercury for every 10 degrees
was very nearly the ratio of increment, if we except the last 10 degrees, which
is evidently erroneous. Now, it is not a little remarkable, that the same ratio
of increment, extended to 600 degrees, gives an elasticity coinciding very
nearly with the result of my experiment. Thus,300 degrees gives an elasticity
of 147 inches of mercury.
|
350 |
252 |
|
400 |
382 |
|
450 |
537 |
|
500 |
717 |
|
550 |
922 |
|
600 |
|
|
767 |
1152 |
[Flaxseed
oil contains a portion of water, and will boil at a lower temperature than 600
degrees: this may have led Mr. Stevens into an error; but whether the result
which he has drawn be true or not, experience shows that we can obtain any
power that we would attempt to hold in our boilers, and sufficient for any
purpose. In the year 18011 constructed, for the purpose of making experiments,
a small boiler of cedar wood, 12 inches diameter and 20 inches in height,
strongly hooped with iron: inside of this cylinder was put a cast iron furnace
7 inches diameter at the lower and 320, then to 30 inches diameter, just as
large as will be quite safe to hold the power. Then he may feel fully confident
that it will answer his expectations, and that he may work with a load on his
safety valve of 100 or perhaps 200ibs. to the inch, as well as Evans. Dr. Coxe
saw him have the whole in actual operation, and it has performed well two years
already. Mr. Stevens, in his note, shows that he misunderstood me respecting
the load on the safety valve, viz. 281bs. lessening the fuel to one-third. He
has here spoken learnedly on the principles which I had explained long before
to Dr. Coxe.]
I
have lately been engaged in making a number of experiments, to ascertain the
elasticity of steam at the temperature of boiling oil. In making similar
experiments about two years ago, I employed a lever to keep down the valve,
with a weight suspended thereon like a steelyard. This mode of operating was
necessarily inaccurate. I now pursued a plan which was not liable to the same
errors. A brass tube about ten inches long, and about one inch diameter, was
first fixed in a perpendicular direction in an iron vessel containing common
paint oil; on the top of this tube, the surface of which was perfectly flat, a
valve was accurately fitted; the bore of the tube is precisely three-eighths of
an inch in diameter; a tea-spoonful of water was then poured into the tube
(which filled it about one-fourth full), the valve raced thereon, and loaded
with 73 lbs. After the oil had been made to boil some time, about three fourths
of a pound was gradually removed. To do this readily I made use of nails. An
explosion then took place, but without much noise, as the steam was but barely
able to make its escape.
This
experiment was tried repeatedly with little variation; so that the elasticity
of steam, at the temperature of boiling oil, may be depended on, as being
ascertained with a considerable degree of accuracy. I am certain it cannot
deviate from truth, more than one part in a hundred.
ÉÉÉthan
280 degrees, at which temperature the elasticity of steam was found equal to
about four times the pressure of the atmosphere. By experiments which have
lately been made by myself, the elasticity of steam at the temperature of
boiling oil, which has been estimated at 600 degrees was found equal to upwards
of 40 times the pressure of the atmosphere.
To
the discovery of this principle or law, which obtains when water assumes a
state of vapour, I certainly can lay no claim but to the application of it,
upon certain principles, to the improvement of the steam engine, I do claim
exclusive right. It is obvious that, to derive advantages from an application
of this principle, it is absolutely necessary that the vessel or vessels used
for generating steam should have strength sufficient to withstand the great
pressure arising from an increase of elasticity in the steam. But this pressure
is increased or diminished in proportion to the capacity of the containing
vessel. The principle then, to which I claim exclusive right, consists in
forming a boiler by means of a system, or combination of a number of small!
vessels, instead of using, as in the usual mode, one large one; the relative
strength of the materials of which these vessels are composed increasing in
proportion to the diminution of capacity. It will readily occur that there are
an infinite variety of possible modes of effecting such combinations; but, from
the nature of the case, there are certain limits, beyond which it becomes
impracticable to carry our improvements. In the boiler I am about to describe,
I flatter myself the improvement is carried nearly to the utmost extent the
principle is capable of.
SPECIFICATIONS
Suppose
a plate of brass, of one foot square, perforated by a number of copper tubes of
an inch diameter and two feet long, the other ends of which to be inserted in
like manner, into a similar plate of brass: the tubes, to insure
inches
diameter at the upper end, with a flange 12 inches diameter at each end, which
served as heads for the wooden cylinder: I fixed a safety valve and cock in the
upper end. The space between the furnace and wooden cylinder contained the
water which surrounded the fire. A small fire in this furnace soon raised the
power of the steam to such a degree as to lift the safety valve loaded with
1521bs. to the inch. I then opened the cock, regulating it so as to keep the
valve just lifting. The quantity of steam which continued to escape while the
fire was kept up, and the force with which it issued, was astonishing. The
degree of heat which produced this immense power did not in the least injure
the cedar wood. No further experiments were necessary to prove the
practicability of the application of my principles.]
COPY OF MR. STEVENS'S PATENT AND SPECIFICATION.
To
all to whom these presents shall come, greeting:
I
certify that the annexed writing is a true copy of the specification of a
patent granted to John Stevens, duly compared with the original on file in this
office.
In
faith hereof, I, James Madison, Secretary for the department of State of the
United States of America, have signed these presents, and caused the seal of my
(L. S.) office to be affixed hereto, at the city of Washington, this sixteenth
day of January, A. D. 1805, and in the twenty-ninth year of the independence of
the said States.
JAMES
MADISON.
From
a series of experiments made in France, in 1790, by Mr. Belancour, under the
auspices of the Royal Academy of Sciences, it has been found that, within a
certain range, the elasticity of steam is nearly doubled by every addition of
temperature equal to thirty degrees of Fahrenheit's thermometer. These
experiments were carried no higher
ÉÉ..one
year before he took out his patent, far exceeding every application of steam
before known or used.And Mr. Stevens, well knowing that I claimed the exclusive
right to the Invention, attempted to secure to himself the exclusive right of
using this my discovery, which had cost me 2000 dollars in cash to put in
useful operation, besides my time which I cannot rate at less than another
thousand dollars. But he says he has been twenty years hard at work, spent
20,000 dollars, and succeeded in nothing; therefore he thinks that he is
entitled to his claim. The date of his patent (April 11th, 1803) is two months
after Dr. Coxe had called on me. He has specified nothing but what was in use
before; and all his projects, that he has yet mentioned, on which he has spent
his labour and money1 have been tried by others long ago.]
OLIVER
EVANS'S REPLY.
extracted
from the Medical Repository.
PHILADELPHIA,
APRIL 13, 1805. SIR,
AT
the several times which Dr. Coxe called on me at your request, to obtain
information respecting the construction and principles of my improvements on
steam engines, I asked him what was the object of your numerous and pointed
questions. Does he intend any interference with my invention? He answered, that
you were a gentleman, and was making experiments for your amusement that
therefore I need not apprehend any interference. Having received this
assurance, I communicated freely, answering all your questions, and explained
the principles without reserve, as I have done for twenty-one years past (ever
since I first conceived the principles) to every gentlemen whom I conversed
with on the subject; and when I was informed by Dr. Mitchill, in December or
January last, that you intended to comment on the paper which I had laid before
each member of congress individually, to show the the differ-
17
their
tightness, to be cast in the plates. These plate are to be closed at each end
of the pipes by a strong cap of cast iron or brass, so as to leave a space of
an inch or two between the plates and their respective caps. Screw bolts pass
through the caps into the plates. The necessary supply of water is to be
injected by means of a forcing pump into the cap at one end, and through a tube
inserted into the cap at the other end the steam is to be conveyed to the
cylinder of a steam engine. As the boiler now described embraces the most eligible
mode that has yet occurred to me of applying the principle, it is unnecessary
to give descriptions of boilers less perfect in form and construction,
especially as these forms may be diversified in a thousand different modes.
(Signed)
JOHN STEVENS.
signed
in presence of as,
JOHN
KEESE,
CHARLEs
T. KEESE.
The
patent is dated April the 11 th 1803.
[Mr.
Stevens in his specification, confines his invention to his boiler, which was
patented by Mr. James Runisey, August 6th, 1791. Mr. Runisey's words in his specification
are as follows: " That is new modes of generating steam in greater
quantities, to a greater degree of expansion, and with much less expense of
fuel, than by any mode ever before known, by means of a boiler consisting of,
or formed by, homogeneous incurvated tubes, connected together and composed of
metal least subject to corrode." But Mr. Runisey failed in the application
of the principle, therefore, if Mr. Stevens has made any improvement which will
cause it to answer the purpose, he is intitled to a patent. These are the
principles on which he claims the exclusive right of using strong elastic
steam, which was not known to be useful, nor used to any working engine, until
I discovered the means of application, and had it in actual operationÉ.
Now,
sir, what benefits do you expect to arise from your having laid me under the
necessity not only of defending my character, but my interest? Shall we
criminate and recriminate each other in public, until we give good people cause
to pronounce us fools? I wish to employ my time to a more useful purpose. To be
sure, you have greatly lessened the force of your remarks, by informing us that
you have been hard at work for twenty years, and expended 20,000 dollars, and
have not yet derived one shilling from all your various schemes and projects.
Surely, sir, this experience of your's was sufficient to have taught you, that
you are not qualified to pass judgment on the works of those who have been
successful. It is at least sufficient to convince other people. Can you point
out one single instance wherein the man whose work you condemn has failed of
success in bringing into operation and use any thing he once attempted?
In
answer to your charge I might retort on you as follows:
1.
You say I am in pursuit of an ignis fatuus; but experience has taught me, that
many who think themselves wise have said, and will say the same thing, until
they either understand the principles, or see them in operation.
2.
I was not publishing, but only writing to each individual member of congress,
therefore there was no need of mentioning Captain Savary's application of
strong elastic steam in his first attempts; but you have omitted to mention (I
will not say through design) that he soon gave it up for want of a true
knowledge of the principles which only could direct to a useful application. I
was showing the difference of the principles and powers between Watt and
Bolton's steam engine (which has long been esteemed the best) and my own, to
show how far my principles exceed their's, as justly to entitle me not only to
an exclusive right for using them, &c. but to the fostering aid of
congress, so far as to protect me in the exclusive enjoyment of my improvements
on mills for another term that I might appear the presence in principle of the
best English steam engines and my own, (which I did not write for publication,
nor did I publish it) he then told me that you would treat the subject like a
gentleman; therefore I rested so perfectly easy that I did not peruse your
comment until yesterday, three months after its date. I assure you I was not a
little surprised and disappointed to find, that as far as your credit and
influence may extend as a scientific character, your comment tends to
stigmatize me, to impede the introduction of my improvements, by increasing the
doubts in the minds of the people about the principles of my engine, which has
been in actual practice and highly useful operation for three years, far
exceeding all others of which I have any knowledge. Although the working cylinder
is only 6 inches in diameter and length of stroke 18 inches, she will grind 400
bushels of plaster in twenty-four hours, or saw 200 feet of marble stone; and
when my principles are fairly and fully put in operation, the work will be
doubled, or perhaps trebled.
1.
You say I am in pursuit of an ignis fatuus.
2.
You indirectly insinuate that I, through design, omit to mention that Captain
Savary wrought his engine with strong elastic steam.
3.
That I have dexterously assumed to myself a principle for which you obtained a
patent two years ago.
4.
You attempt to turn my ideas and my further proposed improvements into
ridicule.
5.
You say I have assumed very erroneous principles in my improvements of my steam
engines, as well as my perpetual still.
6.
You say that I have exaggerated enormously the strength of my boiler, and
endeavour to show that it is incompetent to the task I assign to it.
7.
You say that the application of the discoveries made by Dr. Black, twenty years
ago, respecting latent heat, and the very important law of increment, developed
by certain gentlemen, to the improvement of steam engines, was obvious;
therefore I can have no well grounded claim.
ÉÉ.ply
the net proceeds to defray the expenses of extending the use and introduction
of my improved steam engine, as well as of the expensive experiments, which
will be necessary to put in practice my further proposed improvements, which I
have specified, and I do assure you, sir, you do not show you understand them.
3.
Have I been half so dexterous as yourself; who sent Dr. Coxe to view my
principles, then in operation and use one year, (publicly exhibited and
explained to every one who inquired after the principles) and to put a number
of questions to me, which drew in answer, a full explanation of the
construction and principles of my invention, and 'which, when you were in
possession of; the improvement became obvious to you, and you went and
attempted to take out a patent for, and assumed it to yourself; but herein you
have failed for want of a competent knowledge; besides you are not the original
inventor.
4.
Do you really believe that the fire of volcanoes is kindled by atmospheric air?
If you do, please to point Out to us the apertures by which it is possible for
the air to enter against a force which casts up rocks two thousand feet high;
or else show why fuel, which burns in one place without the aid of atmospheric
air to kindle it, will not so burn in another place with the aid it has, be
that what it may; or why air cannot be substituted instead of that unknown aid
in the manner which I have proposed.
5.
Are you sure you are competent to assert, that I have assumed very erroneous
principles, while you show you do not understand them yourself? or that Mr.
Dalton's experiments are more accurate, or the result he has drawn nearer the
truth than those of the editors of the Encyclopedia? That Dalton, as well as
yourself, is wrong, is evident, because, if we continue his scale of diminution
of the ratio, the increase of elasticity by the increase of heat will entirely
encase long before the power be sufficiently augmented to burst the cannon, as
stated by the earl of Worcester.
6.
Have you any rule for ascertaining the power exerted to burst a boiler, by
which you can tell how enormously I have exaggerated the strength of my boiler?
The rule by which you seem to have calculated is really false, and your
calculations are a specimen of your qualifications, as there is, unfortunately
for you, no solution of this useful problem to be found in any book that I can
find; you must, therefore, have recourse to your own inventive genius, and it
was absolutely necessary you should possess this knowledge to enable you to
arrange a steam engine.
7.
Was it not equally obvious, that a pipe of 1 inch diameter, would expose more
surface to the heat of the fire, and bear a greater elastic power of steam, in
proportion to its contents, than one of 20 inches diameter. But who ever made a
boiler consisting of pipes of 1 inch only in diameter, to work a steam engine,
until it was done by John Stevens, Esq. of Hoboken; excepting only the late
ingenious colonel James Rumse,-, about fourteen years ago in the city of
Philadelphia, and afterwards in the city of London. His patent is dated August
the 6th, 1791, which will expire the 6th day of August next; he, however, as I
have been informed, found it would not do in practice, and therefore gave it up
as an ignis fatuns. But shall this discovery, or patent of his, make your claim
groundless, or prevent you from pursuing the same ignis fatuus, for which you
took out a patent two years ago? I hope not, or else there could be but few
well grounded claims.
Your
ignorance of the principles of my invention has caused you thus far to commit
and set yourself in the way as an obstacle to the introduction of the most
useful improvements ever made on steam engines: but you have one consolation;
this will serve more to perpetuate on memory than your twenty years hard work,
and 20,000 dollars risked.
You
may rest perfectly easy in the possession of your boiler, as you have specified
it; and of your scheme of' experiments, would accomplish the great ends of
propelling boats and land carriages. We need not contend, the range is
sufficient for us both; let us unite our resources. If I had possessed the sum
to expend twenty years ago that you say you have already expended, I do believe
that my inventions and improvements might, at this day, have been doing the
labour of at least 100,000 men in this country.
When
the blind man took the lame one on his back, they both travelled safely; but I
am as doubtful of the success of your project of a boiler as you are of my
volcanic one; and think I could convince you of the great probability of the
success of my plan of pouring all die heat of the fire into the water, instead
of passing up the chimney, which is all that can be possibly got from the fuel,
and would be lighter, and far more durable and easier repaired than your's; but
I will not risk the expense of the experiments until there be a better prospect
of reward. I have made a small boiler on that principle, which appeared to
answer well; all the heat of the fire entered the water to generate steam,
which, united with the elastic fluid, generated by the consumption of fuel, formed
the agent to work the engine.
MR.
STEVENS'S REPLY.
Extracted
from the Medical Repository.
THE
only part of the above letter, which I consider sufficiently important to
require any notice on my part, is the charge Mr. Evans has thought proper to
bring forward against me, of sending Dr. Coxe to him to steal his invention;
for which he is pleased to say, " I have taken out a patent, and assumed
it to myself." To repel so odious a charge, it will be necessary to go
into a detail much longer than I could wish.
Mr.
Evans, in the above letter, admits unequivocally, that he has no claim whatever
to the boiler specified in working one of Watt and Bolton's by the steam of one
of my engines after it leaves it ; for I can produce more effect from the steam
by one cylinder than I can by using two, as you propose: and of your mode of
distilling by steam, as described in your comment, I would wish to know when
you invented it. But if you will attempt to infringe my patent, the best way
will be to decide the matter in a court of law, without troubling the public
therewith. I am sorry to be obliged to spend my time thus, as I am engaged in
writing for the press, a small treatise on the principles and powers of steam,
and of my own improvements, which, when published, many things will become
obvious to you that are not so now but then you can easily show that they were
so for twenty years past, because my deductions are all drawn from the
experiments, discoveries, reasoning, &c. of Dr. Black, and other
philosophers, who have lived ~ wrote before me.
I
might, in the same time thus spent, have discovered or wrote something useful.
To
conclude, seeing you have so dexterously procured your injurious remarks a
place in the Medical Repository, I will thank you to obtain a place in the same
work for this letter, or adopt any means you please to place me on as good
grounds as you found me, and you will much oblige,
Sir,
your humble servant,
OLIVER
EVANS.
JOHN
STEVENS, Esq. of Hoboken,
near
New-York.
p
5 After the publication of the above, and you quit all claims to my inventions,
I shall consider myself redressed, and shall be willing to correspond with you
on friendly terms. We should assist, instead of injuring each other.
If
your plan of a boiler should prove useful in practice, and generate more steam,
with equal fuel, than mine, I shall rejoice at the improvement, which, united
with my improve-ÉÉ.
strength
of one atmosphere to two than was necessary at first to raise it to one ; or,
in other words, if we add to steam as much more heat as it may already contain,
we shall make it more than twice as elastic."
Here,
then, we find that the advantages of using strong steam were suggested and
pointed out by me before I heard, or, indeed, could have heard of Mr.
Belancour's experiments.* But after it had been satisfactorily proved by these
experiments, that the increase of the elasticity of steam was in a far greater
ratio than the increase of heat, it could not be imagined that I should have
remained insensible of the immense importance of the application of this
principle to the improvement of the steam engine. The truth is, that ever since
the period above mentioned, I have been more or less engaged in various
projects for applying this principle to advantage. To enumerate and describe the
boilers I have constructed on different plans, with a view to effect this
object in the most convenient and eligible mode, would be tedious and
unnecessary, more especially as Mr. Evans does not seem disposed to dispute the
right of invention of any specific improvements of the steam engine; but
generally the exclusive right of applying to this purpose the above mentioned
principle.
[His
words, on November 23, 1790, show the extent of his knowledge of the principles
at that time to have been mere conjecture and supposition: for if Mr. Blakey
had succeeded in his attempt to apply the principle, by the intervention of
oil, in the year 1700; or if Captain Savary or the Marquis of Worcester had
applied their strong elastic steam to move a piston in a cylinder; or if Mr.
Newcomen had applied Savary's boiler to generate strong elastic steam, to
propel his piston, the work would have been done, andÉÉ
These
experiments were made in Paris, in 1790, and were never heard of by me until
they appeared in the new edition of the encyclopedia Britannica.
my
patent. What, then, is it I have stolen from him ~ He affects, it seems, to
take it for granted, that the idea of using steam at a high temperature and
great elasticity, never occurred to me before I had obtained information on
that head from Dr. Coxe. But the following extract from a statement,* presented
in Feb. 1791, to the Board of Commissioners appointed to adjust and settle
interfering claims for exclusive patent rights, will prove, in the most
satisfactory manner, that the idea of the great advantages resulting from using
steam of high temperature and great elasticity, had actually occurred to me
many years ago: and, I should suppose, even before Mr. Evans had thought of it
himself. In describing what I then thought an improvement of the steam engine,
which, at this time, it is unnecessary to explain, I make use of the following
words:
For
if; by the intervention of water or oil, we should be enabled to make use of
steam of four times, for instance, of the usual strength, the advantages we
should derive from it would be very great.
1.
A cylinder of 2 feet diameter would be as powerful as one of 4 feet diameter.
2.
There are sufficient grounds to induce us to believe, at least, that less heat
is required to raise steam from the
This
statement was drawn up in conformity to the following notification:
Philadelphia,
November 23, 1790.
Some
of the claims for patents, founded on the supposed discovery of new
applications of steam to useful purposes, not having been stated precisely as
to be satisfactory to the board, and it being their wish to hear all those
claims together,
Ordered,
That the first Monday of February next be appointed for tile hearing of all
parties interested; that notice be given to John Fitch, James Rumsey, Nathan
Read, Isaac Biggs, and John Stevens, of this order; and that each of them be
required to transmit in writing to the Board, a precise statement of their
several inventions, and of the content thereof.
extract
from the Miniltes,
HENRY
REMSEN, Jun..
ÉÉÉ..might have saved Mr. Stevens 20,000
dollars, besides much study and labour: but it is left for us to contend about.
Admitting all Mr. Stevens's statements are true, then the facts appear to be as
follows, viz. In the year 1784, 1 conceived the means of applying the
principle, and in 1786 I explained it to the legislature of Pennsylvania, but
they refused to grant me the patent. Early in 1787, I explained it to the
legislature of Maryland, and obtained the exclusive right of using it for
fourteen years, but did not commence the execution for seventeen years after my
first discovery of the means of applying the principle, not being able to find
any one willing to join me in risking the expense. Mr. Stevens asserts, that in
1790 he had some distant ideas of the existence of the principle, and that he
had been at work which he continued for twenty years, but did not succeed. At
the end of seventeen years I went to work, put the principles in operation, and
succeeded beyond my expectations. A gentleman having seen the engine at work
was astonished at its operation, and undertook to announce the discovery to the
public, stating its great performance. This Mr. Stevens gets sight of, sends to
Dr. Coxe, contains a full account of the construction of my engine, and
explanation of my principles. He then took out a patent, attempting to secure
to himself the exclusive right of using the discovery on certain principles;
which I never heard of his having done, until I read the specification
published by himself, in his unprovoked attack on me. Being ashamed immediately
to adopt my engine exactly, he spent one year more (the last of his twenty
years) on projects of his own, but could not succeed; and was at last reluctantly
compelled to follow me exactly, by adopting every improvement which I had made9
calling it Bolton and Watt's engine. If Mr. Stevens had really understood the
principle, he might in the course of his twenty years labour have put it in
operation before I began, and then his claim would have been much better
supported.]
But
were we even to admit that Mr. Evans was really the original discoverer of this
all-powerful principle he would, l apprehend, even in this case, find it
impracticable to secure against infringement a claim of exclusive right to the
application of it. How, I would ask him, could he prevent me or any other man
from loading at pleasure the safety valve; a practice coeval with the first
invention of the steam engine itself? Captain Savary's engines were capable of
raising water from 100 to 200 feet high; consequently he was in the habit of
loading his safety valve with 50 to 100 lbs. on the square inch.
In
this paragraph Mr. Stevens has discovered his original intention in making the
attack, viz. to destroy my exclusive right totally. Mr. Watt met with many such
attacks. He could not prevent any person from condensing their steam, a
practice coeval with the use of the cylinder and piston; but fortunately for
him, as Mr. Stevens did not set as judge, he did prevented others from
condensing their steam in his improved way, and confined them to what was
before known and used. If Mr. Stevens were to set as judge on my case, I should
have little hope; but with any other judge or jury I fear not to risk the
matter. Although I do not expect to prevent any one from loading their safety
valve, in such engines and for such purposes as were before known or used, yet
if they attempt to use great elastic power of steam, die application of which I
have discovered, explained and made known at a great expense, I expect to be
able to prevent Mr. Stevens himself or any other person from doing so. If not,
no patent can be supported; for surely none is better founded. It was be seen
that I have made greater improvements on steam engines than any other man;
removed the obstacles, and opened a clear and distinct view to still far
greater improvements. Compare them with Bolton and Watt's improved Newcomen's
engine: They contrived to condense the steam in a vessel separate from the
cylinder, and to put steam in above as well as below the piston, thereby
obtaining a double stroke: their plan required the addition of an air-pump,
which they applied:
ÉÉÉ.their
engine proved more powerful, was easier governed, required only one-fourth the
fuel to do die same work, and was pronounced the greatest of human inventions.
I have made a total change in the system: I have applied the Marquis of
Worcester's discovery, (after its having been abandoned one hundred years) to
move a piston in a cylinder; discovered the great advantage of using strong
elastic steam, demonstrated, explained and made it known: I have dispensed with
the heavy lever beam, condenser and air-pump, and simplified the construction
of the boiler, cylinder, piston, and working gears: my plan required a small
forcing pump to supply the boiler, which was applied. Thus, I have produced an
engine ten times as powerful, more governable, and easier varied to suit any
task assigned to it than Bolton and Watt's: it can be constructed at half the
price, and will expend only one-third the fuel to do as much work as their's,
and is applicable to every purpose to which their's can be applied, besides a
great many more. I have specified and explained by drawings, five differently
constructed engines all of which will work well to produce immediate circular
motion, on my new principle of confining and retaining the steam to increase
the heat and elasticity; but these are worth nothing if wrought on the old
principle. Indeed, I fear there is nothing left for Mr. Stevens to discover in
the art. I hope I am not guilty of egotism in stating facts, when the public
good and my own interest require it.]
And
now, I hope, I have done with Mr. Evans. Nothing less than the necessity of
vindicating myself against the foul aspersion he has thought proper to bring
forward against me, could have induced me to have set my pen to paper. I still,
however, entertain the most favourable opinion of Mr. Evans's candor and
integrity, and am disposed to think, that, when his passion shall have
subsided, he will sincerely regret the gross abuse he has bestowed on me; and
probably the time is not far distant, when he will be convinced of the truth
and justness of the remarks I have taken the liberty of making on his various
projects, and the angry strain of invective which he now indulges himself in,
will ultimately give grace to grateful acknowledgments for the services I have
rendered him.
The
world are greatly indebted to Mr. Evans for his ingenious improvements of mill
machinery; and I sincerely hope, that his distinguished mechanical abilities
may still continue to be exerted in a way best calculated to promote his own
individual interest, and, at the same time, render essential benefits to the
community at large.
[Here
Mr. Stevens hopes to have done with me; but why did he begin? What prompted him
to make such an unprovoked and illiberal attack? Is truth, when stated by me,
foul aspersion; and error, when advanced by him, truth and meekness? I did not
say he sent Dr. Coxe to steal my invention; this he has discovered himself, and
he is certainly best acquainted with his own motives. Of Mr. Stevens's candour
I am doubtful, but I hope my suspicions may prove groundless. Why did he not
send me a copy of his reply before he published it, as I had done by sending
him my letter in answer to his remarks? Had he done this, and not attempted to
hold an undue advantage, after being himself the aggressor, he might have been
done with me. "I still, however, entertain the most favourable
opinion" of Mr. Steven's patriotism: " the world are greatly indebted
to him for his" laudable pursuits; and I hope that when I discover the
great good he has done me, by " the remarks he has taken the liberty of
making on my various projects," that my "angry strain of invective
will give place to grate full acknowledgments." I sincerely wish Mr.
Stevens success in his laudable undertakings, and that they may prove
beneficial "to the community at large."
É.it
to boil and the ether is converted into vapour, carrying)g off the heat to fill
the vacuum. This is a positive proof that a vacuum will receive and retain in a
latent state more heat than a plenum.
These
principles may probably be applicable to useful purposes. For instance, to cool
wholesome water, such as that of the Mississippi, rendering it palatable for
drinking, to supply the city of New-Orleans; or of the Schuylkill to supply the
citizens of Philadelphia. A steam engine may work a large air-pump, leaving a
perfect vacuum behind it on the surface of the water at every stroke. If ether
be used as a medium for conducting the heat from the water into the vacuum, the
pump may force the vapour rising from the ether, into another pump to be
employed to compress it into a vessel immersed in water; the heat will escape
into the surrounding water, and the vapour return to ether again; which being
let into the vessel in the vacuum, it may thus be used over and over
repeatedly. Thus it appears possible to extract the latent heat from cold water
and apply it to boil other water; and to make ice in large quantities in hot
countries by the power of a steam engine. I suggest these ideas merely for the
consideration of those who may be disposed. posed to investigate the
principles, or wish them put in operation. And, lest I should be thought
extravagant, as was the case with the Marquis of Worcester, I give aÉÉÉ.
DESCRIPTION OF THE MACHINE.
Make
an air-pump and close the lower end of the cylinder by connecting it with a
globular glass vessel, if metal will not answer as well: fix the lower end of
the cylinder of this pump, so that the glass vessel shall be immersed in the
water that is to be cooled, and which is to be contained ~ a tight vessel. Near
to this pump fix another much smaller, called the condensing pump, and connect
it with a small vessel, called the condenser, immersed in water, fixing off
from the water by the steam, composed from a very small part off the water, yet
it is not the steam that contains the 1000 degrees of heat in a latent state,
but the space which it occupies; this quantity of heat is necessary to heat up
that large space to the temperature of 212 degrees; and the truth is, that only
212 degrees of heat are a necessary constituent part of steam, under the
pressure of the atmosphere. It is true that if the heat that is carried off by
the steam formed by 1 cubic inch of water expanded into 10,000 or 14,000 cubic
inches space, was to be returned into 1000 cubic inches of water, it would
raise the temperature of the whole mass 1 degree; but if the heat that is
contained in 1 cubic inch of the space occupied by the steam, be returned into
1000 cubic inches of water, it appears by this statement that it would raise
the temperature of the water but part of a degree.
The
steam of boiling water exactly balances the weight of the atmosphere: if
therefore we have occasion to fix a pump to raise hot water, we must place no
dependence on the pressure of the atmosphere to force it up through the lower
valve, (as it does when the water is cold) because the steam rising from water
of the temperature of 212 degrees, will fill the vacuum that would be formed by
the working of the pump, and exactly balance the pressure of the atmosphere and
prevent the water from rising. In such cases the lower valve must be placed
below the surface of the hot water that is to be raised.
Water
boils in vacuum at the temperature of 70 deg. and vapour may by compression be
reduced to the fluid from whence it arose: hence we may infer, that water will
keep cooler in vacuum than when exposed to the pressure of the atmosphere. If
an open glass vessel be filled with ether and set in water in vacuum, the ether
will boil rapidly and rob the water of its latent heat until it freezes. It is
not right to say that the ether becomes so cold that it freezes the water
around it. The heat in the water enters the ether, causingÉÉÉ
ÉÉ.valve
between them. Connect the upper end of these working cylinders by a pipe with a
valve therein at the top of the exhausting pump, and connect the bottom of the
condenser with the glass globe, by a small pipe, in which insert a cock1 called
the ether-cock. The piston rods of the pumps must work through stuffing boxes
made air-tight, and each piston must have a valve fixed in it, one to shut
downward and the other upward: work these pistons by a lever that is to be put
in motion by a steam engine or any other power.
THE OPERATION.
Fill
the glass globe with ether, ~o that the piston will touch its surface at every
stroke; expel the air from the pumps and condenser, making a complete vacuum in
them. Set the machine in motion and every time the piston rises the exhausting
piston leaves a perfect vacuum behind it:
ÉÉ.the
ether then begins to boil and carry off the latent heat from the water; the
steam of the ether fills the vacuum, which is again exhausted by the pump, and
driven into the condensing pump which compresses it in the condenser, forcing
out the heat which robs the vapour of its essential constituent part, and
reduces it to ether again; the ether-cock being opened just sufficient to let
the ether return to the glass globe to undergo the same operation; and so on ad
infinitum. The machine might be simplified by connecting the top of the
exhausting cylinder with the condenser, dispensing with the condensing cylinder
and piston. The condensation might be sufficiently effected by the exhausting
cylinder and piston alone forcing the vapour into the condenser. If the air not
expelled it will be forced into the condenser, and remain above the ether formed
there without injuring the working or the effect of the engine: but I presume
the condensing pump would be necessary to carry the principle to such extent as
to boil water by the heat extracted from cold water. A small pump may be fixed
so as to be worked by the same lever, to extract the water from the vessel as
fast as 'necessary after it is cooled. The vessel may be kept full by the
pressure of the atmosphere forcing the water through a valve at the bottom.
CONCLUSION.
Many
persons think that new inventions and discoveries are made by accident, without
labour or expense: some may have such a gift. It was a saying among the
ancients that " truth lies in a well;" and may we not say that reason
and experience are the means by which we draw it out. It has been by the most
intense study that I have made discoveries. After having a faint glimpse of the
principle, it was with may be and tedious.; steps that I attained a clear and
distinct view. I received great assistance from the result of experiments made by
others, which arc to b found in scientific work; and righted believed that if
government would, at the expense of uncertainty, employ ingenious persons, in
every art and science, to make with care every experiment that might possibly
lead to the extension of our knowledge of principles, carefully recording the
experiments and results so that they might be fully relied on, and leaving
readers to draw their own inferences, the money would be well expended; for it
would tend greatly to aid the progress of improvement in the arts and sciences.
I
now conclude, and renounce all further pursuit of inventions and discoveries,
at least until it shall appear clearly to be my interest; lamenting that it
should so often prove unprofitable, and even ruinous as it has been to many. I
at the same time believe, that more good frequently results to the community
from intellectual than corporal labours; yet one pair of hands is worth two
mechanical or philosophical heads to the individual himself. I purpose,
however, to attend to the improvement of my steam engine, to render it suitable
for the various purposes for which it may be required.