Original
source: http://www.history.rochester.edu/steam/evans/1805/
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 Steam Engine on new principles, rendering it much more
powerful, more simple, less expensive, and requiring much less fuel than an
engine on the old construction. |
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. A
description of four other patented inventions. |
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
Advertisement
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.
YOUNG STEAM ENGINEER'S
GUIDE.
ARTICLE I.
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 many 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 discovering 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.1
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 the 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 of the simple principle impossible, even after it is
applied to engines daily in operation before our eyes.
ARTICLE II.
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,2 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.
ARTICLE III.
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.3
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;4 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.
See the experiments in the American edition of the Encyclopedia,
vol.17, from which the following scale is constructed.
|
Degrees of heat in the water adding 30 degrees every step |
Elastic power to the inch are of piston, or safety valve. |
Atmospheres |
|
212 gives 30 |
15 pounds, equal to |
1 |
|
242 30 |
30 |
2 |
|
272 30 |
60 |
4 |
|
302 30 |
120 |
8 |
|
332 30 |
240 |
16 |
|
362 30 |
480 |
32 |
|
392 30 |
960 |
64 |
|
422 |
1920 |
128 |
SCALE OF THE ELASTIC POWER OF STEAM, PRODUCED BY
DIFFERENT DEGREES OF HEAT IN THE WATER.
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.5 So that doubling the heat in the water, may not produce more than
75 or 100 times the elastic power of steam.
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.6
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.
|
Temperature of the water Degrees |
Elastic power of steam lbs. |
Proportional heat to be added to the temperature which the water may be in, to double the power |
|
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 |
|
SCALE OF EXPERIMENTS.
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 to be 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.
ARTICLE IV.
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.7 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.8 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.
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.9
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 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 of boiling water, the more heat is
required to raise it all into vapour; on the contrary, the greater the pres-
sure, 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
shew, 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 contrarry, 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.10 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.
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 11.25.11 (See the scale article 6.)
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 shewn,
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.12
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
eonclude, that the increase of fuel or heat used, will bear no proportion to
the increase of load. (See art. 3,)
ARTICLE V.
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 of 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 inside 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.13
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
inultiplied 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.
|
Diameter of the boiler or tube in inches |
Power to break every ring of one inch of the boiler in anyplace,
in pounds weight, when the steam is1500 pounds to the inch on the safety
valve. |
Thickness of the sheets of good iron necessary to hold the
power, in decimal parts of an inch |
Power exerted on the heads to burst them out, in pounds weight |
|
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 |
|
A TABLE OF THE DIAMETERS
AND STRENGTH OF BOILERS.
|
Diameter oft he boiler or tube in inches |
Strength of boiler to hold the head on, in pounds weight |
Number of inch screw bolts necessary to have strength sufficient
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 numher 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.
ARTICLE VI.
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, 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.
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.)
ARTICLE VII.
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.
ARTICLE VIII.
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.
ARTICLE IX.
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.
ARTICLE X.
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 water, 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. 14
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.15 It remains for us to improve in the
application of those principles until we discover others, if there be any.
ARTICLE XI.
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 |
322770 |
2400 |
|
Greatest
heat of his small air-furnace |
21877 |
160 |
|
Cast
iron melts |
17977 |
130 |
|
Greatest
heat of a common smith's forge |
17327 |
125 |
|
Welding
heat of iron, greatest |
13427 |
95 |
|
Welding
heat of iron, least |
12777 |
90 |
|
Fine
gold melts |
5237 |
32 |
|
Fine silver
melts |
4717 |
28 |
|
Swedish
copper melts |
4587 |
27 |
|
Brass
melts |
3807 |
21 |
|
Heat by
which his enamel colours are burnt on |
1857 |
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 tp
40 |
|
|
Cold
produced by Mr. Macnab at Hudson's Bay, by a mixture of vitriolic acid and
snow |
69 |
|
|
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 |
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.
"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 |
"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 |
ARTICLE XIII.
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 nett 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 NewCastle 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.
|
|
Dolls |
Dolls |
|
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, carring 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 |
ARTICLE XIV.
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
Secretary 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.
ARTICLE XV.
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.16 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,17 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.18 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.
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 the
power is applied, as in the construction 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.19 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.
ARTICLE XVI.
DESCRIPTION OF A STEAM
ENGINE ON TIHE 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 workmg; 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 exeeuted 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.
ARTICLE XVII.
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 in the 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 equalize 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:20 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.
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.
ARTICLE XVIII.
USEFUL INVENTIONS BY
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. They 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. They 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 OI 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 powefful 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 pullies, N 0.
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
dispatch. 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.
EVAN EVANS.
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.21
Plate IV (unavailable) represents
a side view of the machine.
B E the box for holding the earth, fixed to the 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 axel 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 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.
APPENDIX.
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.22 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."
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 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 godgeons 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.
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 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.
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
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-twentieths water 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, consequently engine 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 of
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.23
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.24 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."
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."*
of fuel; but he was obliged to extract the air from the
condenser, 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 principle
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 experiment,
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. Here 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 endeavoured 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,
he was 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 authorised 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
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 had 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 sufficiently 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.
dregs 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 pub15
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
practicability 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 ignis fi~tziu.v.
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 entreat you to take the same liberty
respecting my
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 my 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.)
2nd. " 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 15 lbs. and the force of
vapour of water at 212 degrees is equal to l5 lbs. - 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 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 render 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.
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 |
19.00 |
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 |
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 l3Olbs. 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 1bs. to the 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; 130 1bs. 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 63,OOOlbs. 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,OOOlbs. 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 45001bs. which would require a thickness of only
one-fourteenth of an inch of wrought iron.
[Here Mr. Stevens has magnified, by his calculations, 1500 1bs. to
the inch circumference of my boiler to 90,000 lbs. 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 experiments constructed 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 feet 3 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 there
from, 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 l00
lbs. or perhaps 200 lbs. 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 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 |
|
|
1152 equal
to 767 lbs |
|
That the Saving of fuel must be very great indeed there cannot be
a doubt. Evans states that with a 1021 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 100 lbs. or perhaps 200 lbs. 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 600 lbs. 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 650 lbs 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
[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 1801 I 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.
than 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.]
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 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 difference in 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 11th 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 operation.
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.
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-
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,
and
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 21, 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 Minutes,
HENRY REMSEN, Jun..
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:
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
candour 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."
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 a
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
atmospheie: 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 vaccum 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,
causing
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, so 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.
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.
Notes
1. 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 engines.
2. 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.
3. 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?
4. 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.
5. See the Repertory of Arts, vol i.
series 2.
6. See the American edition of the
Encyclopedia, vol 17.
7. It may pervade all space, which
ancient philosophers held was filled with what they called ether.
8. See the American edition of the
Encyclopedia.
9. See his Lectures, vol.1. See the
celebrated James Watt's experiment to distill in vacuo. Black's Lectures vol 1.
10. See his Lectures, vol 1.
11. 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.
12. See his experiments...Repertory
of Arts, vol. ii. series 2.
13. 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.
14. 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.
15. 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.
16. See the Millwright's Guide, art.
6.
17. Ibid.
18. See the Millwright's Guide,
art.45.
19. 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.
20. 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.
21. 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.
22. 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 thereof. 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 wagon, 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 cannot
make 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 ,Ó 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 telegraph, 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.
23. Which is about 83 pounds, or
about 1 bushel of coals to do the work of a horse.
24. 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.
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Rev.
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