A DOCUMENTARY HISTORY BY ERIC ROBINSON AND A. E. MUSSON

@) 1969 Eric Robinson and A. E. Musson

First published in 1969 by Adams & Dart, 9 Fitzroy Square, London W1

SBN 238.78937.3

Printed in Great Britain by Billing and Sons Limited

Ed. This is a gem of a documentary of letters of Boulton & Watt. As opposed to Tann's collection, this emphasizes the mechanical aspects of the inventions. Much detail on the designs is presented in the testimony of his workers at the patent hearings.

These excerpts cover three of his more important patents for which wash drawings of the patent drawings were included as color plates. The complete Table of Contents is given below with the three excerpted sections hyperlinked to the respective text. JMcV. 1997, 2006

Introduction—p. I

1. Dr. James Gibson to James Watt junior, 8 October 1834—p. 22

2. Professor Robison's Narrative of Mr. Watt's Invention of the improved Engine versus Hornblower and Maberley 1796—p. 23

3. Extracts from James Watt's 'Notebook of experiments on heat'—p. 39

4 Report by Messrs. Hart of Glasgow on conversations with Mr. Watt in 1817. Communicated by John Smith, 19 March 1845 —p. 40

5. Extracts from letters between Watt, Roebuck and others, 1765‑1769—p. 45

6. Draft steam engine specifications—p. 49

7. Dr. William Small to James Watt, 5 February 1769—p. 54

8. Letters Patent, and Specification of Patent, 176 p. 56

9. Matthew Boulton to James Watt, 7 February 1769—p. 62

1Q James Watt to Dr. John Roebuck, 24 September 176~p. 63

11. Dr. John Roebuck to Dr. William SmaD and Matthew Boulton, 26 November 1769—p. 64

12. Mrs. Margaret Watt to James Watt, 22nd ? 1769—p. 65

13. Extracts from letters from John Roebuck junior to James Watt—p. 65

14. 'Comparison of Mr. Blakey's and Mr. Watt's Steam Engines—p. 66

1S. Extracts from letters from Dr. John Roebuck to James Watt—p. 68

16. Copy of the Minutes of the Parliamentary Committee on Watt's Engine Bill, 1775—p. 69

17 1775 Steam Engine Act—p. 76

18. Letter from James Watt to his Father 8 May 1775—p. 80

19. Matthew Boulton to James Watt, March 1776— p. 81

20. J. Smeaton to Boulton and Watt, 5 February 1778—p. 82

21. Extracts from letters from James Watt to Matthew Boulton, 1781—p. 85

22. Matthew Boulton to James Watt, 21 June 1781 —p. 88

23. 1781 Specification of Patent—p. 89

24. James Watt to Gilbert Hamilton, 5 March 1782—p. 95

25. James Watt to Matthew Boulton, 13‑16 February 1782—p. 96

26. 1782 Specification of Patent—p. 96

27 James Watt to James Watt junior, 12 November 1808—p. 109

28. James Lawson and William Murdock to James Watt junior, 14 November 1808—p. 110

29. 1784 Specification of Patent—p. 111

30. 1785 Specification of Patent—p. 122

31. Dr. Thomas Percival to James Watt, 16 September 1786—p. 125

32. Boulton and Watt's Directions for erecting and workmg the newly‑invented steam engines, 1779 —p. 126

33. List of improvements chiefly mechanical not secured by patent'—p. 155

34. James Watt junior to F. Arago, 13 October 1834—p. 155

3S. Mr. Hornbloweis Case Relative to a Petition to Parliament for the extension of the Tcrm of his Patent'—p. IS8

36. Short Statement, on the Part of Messrs. Boulton and Watt, in Opposition to Mr. Jonathan Hornblower's Application to Parliament for an Act to prolong the Term of his Patent —p. 160

37. James Watt to Thomas Wilson, 18 July 1792— D. 162

38. Thomas Wilson, 'Address to the Miners of Cornwall’, 1793—p. 163

39. Extracts from Boulton and Watt versus Bull. Copy of the Short‑hand Writer's Notes of the Trial in the Court of Common Pleas, June 1793'—p. 172

40. Extracts from 'Boulton and Watt versus Bull. Copy of Mr. Gurney's Short‑hand Notes of the Argument in the Court of Common Pleas, 27 June 1794'—p. 178

41. General Information respecting the Specification of Patents collected by the Plaintiffs in the Case of Boulton versw Bull. 25 March 1795'— p. 181

42 A View of the Objections which have been at various times urged against Mr. Watt's Specifications'—p. 182

23. 1781 Specification of Patent

This patent was granted on 25 October 1781 and the specification was enrolled on 23 February 1782. The specification describes five different methods whereby the reciprocating action of the steam engine might be converted into rotative motion without using a crank, thus evading Pickard's patent. Of these, the fifth ‑ the 'sun‑ and~•planet' gear ‑ was the one principally adopted by Boulton and Watt, until expiry of Pickard's patent, when they turned over to the crank.

SPECIFICATION OF PATENT, OCTOBER 25TH, 1781, FOR CERTAIN NEW MBTHODS OF APPLYING THE VIBRATING OR RECIPROCATING MOTION OF STEAM OR FIRE ENGINES, TO PRODUCE A CONTINUED ROTATIVE OR CIRCULAR MOTION ROUND AN AXIS OR CENTRE, AND THEREBY TO GIVE MOTION TO THE WHBELS OF MILLS OR OTHER MACHINES.

To ALL TO WHOM these presents shall Come, I, JAMES WATT, of Birmingham, in the county of Warwick, Engineer, send greeting.

WHEREAS His Most Excellent Majesty King George the Third, by His Letters Patent under the Great Seal of Great Britain, bearing date at Westminster, the twenty‑fifth day of October, in the twenty‑second year of his reign, did give and grant unto me, the said JAME S WATT, my executors, administrators, and assigns, His especial license, full power, sole privilege and authority, that I, the said JAMES WATT, my executors, administrators, and assigns, should, and lawfully might, during the term of years therein expressed, make, use, exercise, and vend, within that part of his Majesty's Kingdom of Great Britain called England, his Dominion of Wales, and Town of Berwick upon Tweed, my invention of CERTAIN NEW METHODS OF APPLYING THE VIBRATING OR RECIPROCATING 'MOTION OF STEAM OR FIRE ENGINES, TO PRODUCE A CONTINUED ROTATIVE OR 'CIRCULAR MOTION ROUND AN AXIS OR CENTRE, AND THEREBY TO GIVE MOTION 'TO THE WHEELS OF MILLS OR OTHER MACHINES; in which said recited Letters Patent is contained a Proviso obliging me, the said JAMES WATT, by an instrument in writing, under my hand and seal, to cause a particular description of the nature of my said invention, and in what manner the same is to be performed, to be inrolled in His Majesty's High Court of Chancery within four calendar months next and immediately after the date of the said Letters Patent, as in and by the said Letters Patent, relation being "hereunto had, may more at large appear:

Now KNOW YE, That in compliance with the said Proviso, I the said JAMES WATT do hereby declare that the nature of my said invention, and the manner in which the same is to be performed, is particularly described and ascertained in manner and form following (that is to say): the Eire or Steam Engines whose vibrating or reciprocating motions are to be converted into rotative motions by any or all of the five methods hereinafter described, may be constructed either upon the principles of the steam engines called Newcomen's Fire or Steam Engines, (which have been hitherto most commonly used), or, more advantageously, upon the principles of those newly improved steam or fire engines of my invention, (the sole use and property of which was granted to me by his present Majesty's Royal Letters Patent, dated in the ninth year, and by an Act of Parliament made and passed in the fifteenth year of his reign): or the said engines may be constructed in any other manner or mode wherein a piston or any other part of the said steam or fire engine has a vibrating, alternating, or reciprocating motion: therefore, as for the aforesaid purpose no peculiar construction is required in those parts of the steam or fire engines which concur in and are necessary for the producing the power or active force of the engine, and its vibratory or reciprocating motion, and as steam or fire engines are common and well known machines, it is not necessary to enter into any description of them; I proceed to explain my said newly invented methods of applying the vibrating or reciprocating motions of steam or fire engines to produce a continued rotative or circular motion round an axis or centre, and thereby to give motion to the wheels of mills and other machines, which methods are five in number, and are described as followeth:

Drawing 2, Figures 1 and 2.

IN THE FIRST OF THESE METHODS I employ the power of the steam engine, either directly, or by the intervention of a lever or levers, to pull, push, or press a friction wheel or pulley against the lateral surface of a wheel fixed obliquely upon the primary axis, shaft, or wheel which is to receive the rotative motion; which lateral surface of the said oblique or inclined wheel is represented by the section of a hollow cylinder ABC in the drawing, No. I, figure 1st, cut or sawn off at the angle of sixty‑five degrees to its axis, or at any other angle which may be convenient or useful; and the said friction wheel or pulley J is impelled or pulled by the power of the steam engine against the said lateral surface of the inclined wheel AC, in a direction which is in one way parallel to the said primary axis or shaft DE of the said obliquely cut cylinder or inclined wheel AC; therefore the friction wheel J, commencing its motion at the lowest or nearest part C of the said inclined wheel AC, continues to move in the aforesaid direction nearly parallel in one way to the primary shaft or axis DE, and thereby obliges the inclined wheel AC and the primary axis DE to turn round or revolve on their centre until the highest or most distant part A of the said oblique surface of the inclined wheel AC comes into contact with the said friction wheel J, at which point or time the working beam PP, or other moving part of the steam engine, has moved the length of its stroke, and is disposed to return by the common or other machinery used for that purpose, and the inclined wheel or obliquely cut cylinder ABC has made one‑half of a revolution on its axis, and the rotative motion of the said inclined wheel ABC is continued in the same direction through the other half revolution by means of the descent of the heavy arch G, which was raised by the power of the steam engine at the same time with the friction wheel J, and which, during the returning motion of the working beam of the steam engine, acts upon the inclined wheel AC on the opposite side of the primary axis DE by means of a second friction wheel H, which is carried by a double lever or carriage GF, whose centre of motion is at K, and to the one end of which the heavy arch G, or any other weight, is attached or suspended, and the velocity which the matter of the wheel or cylinder ABC has acquired serves to continue its rotative motion past the points A and C, where neither the steam engine nor the weight G have much action upon it; and when the point C has again come into contact with or has passed the friction wheel J, the steam engine again commences its action, and the motion is continued, as has been recited, and the mill‑work or other machinery which is required to be wrought by this machine is put in motion by the said primary axis, or by the oblique or inclined wheel, or by means of wheels connected with them in the usual manner. This method of producing a rotative motion by means of a friction wheel acting against the lateral surface of a wheel inclined to its axis, admits of many varieties in its mode of application. For I fix the primary axis or shaft either perpendicular or horizontal, or at any other angle of inclination to the horizon which may be required; and I use one or more friction wheels, and I increase or diminish the angle of inclination of the oblique wheel to the primary axis, as the case may require: as therefore I cannot herein represent all those varieties, I have hereunto annexed a drawing or delineation and description of one of the best, (which is applicable to the moving of corn and other similar mills), which drawing is delineated in its true proportions, according to a scale of one‑fourth of an inch for each foot of the real machine, being one forty‑eighth part of the real size. But it must be remembered that I make the machines larger or lesser, and vary the proportions of their parts, as their uses may require. To shew the easiest method of connecting the said new machinery with the piston of the steam or fire engine, on whatever principle it may otherwise be constructed, I have delineated in red the piston and cylinder of a Newcomen's steam engine, (as being the most commonly used). And as the same mode of connection serves equally for all the four following methods herein described, I have not repeated the drawing of the said steam engine, but have only delineated the parts which in these methods connect the new machinery with the old.

MY SECOND METHOD of producing the aforesaid rotative motion consists in applying the power of the steam engine to pull, push, or press a friction wheel or wheels against the external or internal circumference of a circular, oval or double spiral wheel, fixed upon an axis or shaft in such manner that the said axis or shaft shall not pass through the centre of the said circular, oval or double spiral wheel, but shall be fixed nearer to one side of the circumference than to the other, which therefore I denominate an excentric wheel; and the said action of the steam engine and of the said friction wheel or wheels upon or against the circumference of the said excentric wheel, causes it to make one‑half of a revolution, and its motion is continued through the other half revolution by the descent of a weight fixed to or acting upon the said excentric wheel or its shaft, or acting upon another excentric wheel, (fixed to the same shaft), by means of a friction wheel or wheels. This second method also admits of several varieties in its application, of which I have hereunto annexed a delineation of two of the best, strewing the action of the steam engine on the external and also on the internal circumference of excentric wheels, which drawings are delineated and set forth according to their true proportions, by a scale of one‑fourth of an inch for each foot of their real size; but the said machines are also made larger or lesser, and the proportions of their parts varied, according to the uses for which they are required. The excentric wheel, whose external circumference is acted upon by the steam engine by means of friction wheels, is moved as follows‑(see the drawing No. 2, figure 1st): the steam engine pulls up the frame HDL with the friction wheels F, G, against the external circumference of the excentric wheel AB, which causes it to revolve on its axis towards D, ur~•til the point A of the excentric wheel comes to be in the middle between the points of contact of two friction wheels F, G, with the excentric wheel, and the point B has attained the summit of its motion; then the steam engine ceases to act, and the velocity acquired by the excentric wheel AB carries its point B beyond the summit, and the gravity of the unbalanced part of the excentric wheel, which is made equal to half the power of the steam engine, or greater or lesser as may be necessary, causes the excentric wheel to perform the other half revolution, by which motion it pulls down the frame HDL and the end J of the steam engine's working beam, and the point B having past its lowest place, the engine begins to act as before. The action of the steam engine on the internal circumference of an excentric wheel is described as follows: when the engine pulls up the frame DE, (see the annexed drawing, No. 2, figure 3rd), with the friction wheel C, the latter is pressed against the internal circumference of the excentric wheel at H, by which means the wheel is turned round half a revolution, and the point B becomes the vertex; then the engine ceases to act, and the weight of the wheel descending causes it to continue to revolve in the same direction, and completes the revolution, in like manner as has just been described.

Drawing 2, Figures 3 and 4

MY THIRD METHOD of producing the said rotative motion is by means of a rod or rods DB, (see the drawing, No. 3, fig. 1st), one end (D) of which is attached or suspended to the end of the working beam ofthe steam engine, and the other end B to any point of a wheel AEBF, of a circular or any other form, which wheel is fixed at one end of a shaft or axis C; so that by the revolution of the said wheel and the said axis C, the said latter point of fixture or attachment B shall describe a circle round the centre of the said axis, the diameter of which circle shall be equal to the extent of the stroke of the point of the engine's working beam, to which the end D is attached; and the said wheel AEB Fis made so much heavier on one side EBF of the centre than upon the other side A, that the said unbalanced weight EBF shall have an action in its descent equal to one‑half of the power of the steam engine which works the machine, or more or less as required; or in place of putting the weight in the wheel ABF itself, it is put upon a lever or other wheel fixed to the said shaft CC in any other part, or is fixed in any other manner which may serve to make the wheel continue its motion during the return of the piston of the steam engine; and this machine is used as follows: when the point or pin B, which connects the rod DB with the wheel, is a little on either side of the lowest part of its revolution, the steam engine pulls the rod DB, and thereby obliges the wheel to make one half of a revolution, and the unbalanced weight EBF of the wheel, or such other weight as acts upon it during the return of the steam engine, makes the wheel complete its revolution, as has been already recited in the other methods. This third method also admits of several varieties in the mode of execution, for the wheel is sometimes placed so as to turn vertically, (as in the drawing), and sometimes to turn horizontally, and also at other inclinations to the horizon, and the balancing weight is also placed in various situations: I have therefore delineated only one of the most simple and perfect of these methods in the drawing No. 3, hereunto annexed, which is laid down by the same scale with the other drawings of the preceding methods, but the size of the machine must be greater or lesser, and the proportions of its parts varied, according to its use.

Drawing No. 3, Figures 1 and 2

MY FOURTH METHOD of producing the aforesaid rotative motion consists in employing two steam engines to produce a rotative motion in one and the same axis or shaft by any of the aforesaid three preceding methods, or by that which is hereinafter described, and in applying these two steam engines in such manner that the second engine shall begin to act when the first engine has made the said shaft revolve upon its axis one third part of a revolution or thereabouts, and consequently, by the action of both the engines, the shaft makes two third parts of a revolution, and its motion is continued through the remaining one third part of the revolution by the action of a weight properly placed, by which means the rotative motion is maintained in a more equal manner than can be done by a single steam engine. I also apply this method to move two separate or distinct shafts or axles, which are connected in their action by wheel‑work, or otherwise, so that they both must revolve the same number of turns in the same time. As this fourth method must admit of many varieties in its application to any or all of the three preceding or the following methods, all which may be easily understood by explaining its application to one of them, I have only delineated in the drawing No. 4 its application to the third method, as being the most simple, and I have laid down the said drawing according to the same scale with the others. The motion of this machine is explained as under. The pin G of the connecting rod BG, (see drawing No. 4, fig. 2nd), having passed its lowest point, the working beam B ascends by the power of the steam engine to which it belongs, and, by its action on the pin G through the rod BG, causes both the wheels and their common axis to revolve, until the end of the rod BG arrives at the point C, at which time the end of the rod AC, (which is attached to the further wheel), is arrived at the point K, (that is, a point of the further wheel directly behind K in this view), and the centre of gravity of the weight, or heavy sides of the wheels G, J, C, has passed its vertex or highest part at F, and begins to descend towards K; the rod BG continues to act upon the wheels until it arrives at F, where it ceases to act, and the motion is continued only by the gravity of the heavy side of the wheels, or by any other properly disposed weight, until the point C of the further wheel has past its lowest place, and comes into the position directly behind G, when the steam engine belonging to the rod AC begins to act, and continues the motion until it arrives again at C, when the revolution is completed, and the rod B acts as before: the heavy sides of the wheels, or any other weight used to continue the motion, ought to be equal to one‑half of the power of one of the engines, but may be greater or lesser, as suits.

Drawing No. 4, Fig.. 1 and 2

MY FIFTH METHOD of producing the aforesaid rotative motion, (delineated in the drawing No. 5 hereunto annexed), is performed by means of a toothed wheel E, (fig. 1st), fixed upon the end of the shaft or axis F which is to receive the rotative motion; which wheel E is acted upon and made to revolve by means of a second toothed wheel D of an equal, or greater, or lesser diameter, which is firmly fixed to or connected with a rod AB, (the other end of which is attached or hung to the working beam BC of the steam engine, or is otherwise connected with the piston of the said engine), in such manner that the said wheel D cannot turn round on its own axis or centre; and by means of a pin A, which is fixed to, or in the centre of the wheel D, and enters into a groove or circular channel in the large wheel GG, (or by any other proper means), the wheel D is confined so that it cannot recede from the wheel E, but can revolve or turn round the wheel E without turning on its own axis or centre, and the motion is performed as follows. The wheel D being nearly in the position of the pricked circle HH, and so that its centre shall be a little towards either side of the perpendicular line passing through the centre F; the steam engine, by means of the connecting rod BA, pulls the wheel D upwards, and, as its teeth are locked in the teeth of the wheel E, and it cannot turn on its own axis, it cannot rise upwards without causing the wheel E to turn round upon its axis F: when the wheel D is raised so high that its lower edge is come into contact with the upper edge of the wheel E, the engine has completed its stroke upwards, the piston of the engine is disposed to return, and the wheel E, continuing to turn round in virtue of the motion it had acquired, it carries the wheel D past the vertex or highest part, and the gravity of the wheel D, or of the connecting rod AB, or of any other weight connected with them, causes the wheel D to descend on the other side of the wheel E, and thereby continues the motion it had impressed upon it, whereby the wheel D completes its revolution round E; and when the two wheels D and E have equal numbers of teeth, the wheel E makes two revolutions on its axis for each stroke of the engine; and in order that the said motion may be more regular, I fix to or upon the shaft or axis FML, (fig. 2nd), or to or upon some other wheel or shaft to which it gives motion, a heavy wheel or fiyer, to receive and continue the motion communicated to it by the primary movement. AND BE IT REMEMBERED, that in all cases where heavy wheels or swift motions are not otherwise necessary to the uses to which any of the four preceding methods herein described may be applied, a fiyer or heavy rotative wheel should be applied to them to equalise their motion. In figures 3rd and 4th, I have delineated the application of this method to a wheel CC, fixed upon the primary axis, and having teeth upon its inside circumference, which is acted upon by the wheel E in the manner which has just been recited; but as the wheel E has only half the number of teeth that the wheel CC has, the wheel CC will make only one revolution for every two strokes of the engine. The drawings of this fifth method are also delineated according to a scale of one‑fourth of an inch for every foot of the real size of the machine. Figures 1st and 2nd are adapted to a stroke of six feet long, and figures 3rd and 4th to a stroke of three feet long, but I make the machines larger or lesser, and also make such variations in their structure as may serve to accommodate them to their use; as I alter the proportional diameters of the two wheels, and I place the primary axis either horizontally, perpendicularly, or inclined, and I make the wheels of an elliptical, oval, or other form; and sometimes, in place of the wheel D, I use a straight row of teeth or pins fixed to the connecting rod AB, which take hold of the teeth of the said wheel E, and cause it to revolve; some point of the connecting rod being guided by a pin moving in a groove, so as to keep the teeth or pins always engaged in the teeth of the wheel E, and also to keep the teeth of the wheels always engaged in one another instead of the wheel GG and its groove. I use a strap of leather or a link of iron, or other proper material, (such as is drawn at JK), which embraces the axis M or F, and the pin A, and connects them together, and keeps them at their proper distance from each other; and I also make the two wheels E and D without any teeth, but with rough surfaces, so that D turns E by the friction of their circumference alone. BE TT REMBMBERED, that though I have described all these motions as derived or produced from the motion of the end of the working beam of the steam engine, they may also be derived from the vibrating motion of any other part of the steam or fire engine which is found convenient: the end of the working beam appears at present to be the best adapted for that purpose: any or all of these methods admit of the machines being moved with rotative motions in e ither direction, that is, either right‑hand ways or left‑hand ways about, according as the motion is commenced in either of these directions respectively.

Drawing No. 5, Figs. 1 and 2

Drawing No. 5, Figs 3 and 4

IN WTTNESS whereof I have hereunto set my hand and seal, the thirteenth day of February, in the year of our Lord one thousand seven hundred and eighty‑two.

JAMES WATT.

Signed, sealed, and delivered, being first duly stamped, by the within named JAMES WATT, in the presence of

N. BENNETT, Clerk to Mr. Davis of Penryn.

BENI. COT T ETT, Servant to Mr. Davis.

INROLLED in His Majesty's High Court of Chancery, the twenty‑third day of February, in the year of our Lord 1782, being first duly stamped according to the tenor of the Statutes made in the sixth year of the reign of their late Majesties King William and Queen Mary, and in the seventeenth year of the reign of His Majesty King George the Third.

JOHN MTTFORD.

1. P. Y.

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26. 1782 Specification of Patent

This patent was granted on 12 March 1782 and the specification was enrolled on 4 July 1782. It included a number of 'new improvements (i) the use of the expansion principle (with a valve to cut off steam before completion of the piston stroke, thus economizing on fuel), together with various possible devices for equalizing the expansive power; (ii) a double-acting engine, utilizing steam pressure alternately above and below the piston, thus increasing the power and ensuring a more regular motion in rotative engines; (iii) a double or compound engine, comprising two engines, each with its cylinder and condenser, which could either work independently or be combined in such a way that steam employed in the first cylinder could be used expansively in the second; (iv) a toothed rack‑and‑sector connecting the piston‑rod and beam, to permit 'push' as well as 'pull' in double‑ acting engines (a device produced by Watt prior to his parallel motion); (v) a steam‑wheel or rotative engine of similar principle to that patented in 1769.

SPECIFICATTON OF PATENT, MARCH 12TH, 1782, FOR CERTATN NEW IMPROVEMENTS UPON STEAM OR FIRE ENGINES FOR RAISING WATER, AND OTHER MECHAN'CAL PURPOSES, AND CERTAIN NEW PIECES OR; MECHANISM APPLICABLE TO THE SAME.

To ALL TO WHOM these presents shall come, I, JAMES WATT, of Birmingham, in the county of Warwick, Engineer, send greeting.

WHEREAS His Most Excellent Majesty King George the Third, by His Letters Patent, under the Great Seal of Great Britain, bearing date at Westminster, the twelfth day of March, in the twenty‑ second year of His reign, did give and grant unto me, the said JAMES WATT, His especial licence, full power, sole privilege and authority, that I, the said JAMES WATT, my executors, administrators and assigns, should, and lawfully might, during the term of years therein expressed, make, use, exercise, and vend, within that part of his Majesty's Kingdom of Great Britain called England, his Dominion of Wales, and Town of Berwick upon Tweed, my invention of 'CERTATN NEW IMPROVEMENTS UPON STEAM OR FTRE ENGTNES FOR RAISING WATER, AND OTHER MECHANICAL PURPOSES, AND CERTAIN NEW PIECES OF MECHANISM APPLICABLE TO THE SAME;' in which said recited Letters Patent is contained a Proviso obliging me, the said JAMES WATT, by an instrument in writing under my hand and seal, to cause a particular description of the nature of my said invention, and in what manner the same is to be performed, to be inrolled in his Majesty's High Court of Chancery within four calendar months after the date of the said Letters Patent, as in and by the said Letters Patent, relation being "hereunto had, may more at large appear.

Now KNOW YE, That in compliance with the said Proviso, I the said JAMES WATT do hereby declare that the nature of my said invention and the manner in which the same is to be performed, is described and ascertained in manner and form following, (that is to say): my said new improvements on steam or f~•re engines, and my said new pieces of mechanism applicable thereto, are described as followeth. But to prevent misunderstandings and circumlocutions or tautology, I shall first explain the meaning of certain terms which are used in this Specification. FIRST, the cylinder or steam vessel is that vessel wherein the powers of steam or air are employed to work the engine, of whatever form it may be made, though it is most commonly made cylindrical. SECOND, the piston is a moveable diaphragm, sliding up and down or to and fro in the cylinder, and fitted to it exactly, on which piston the powers of steam or air are immediately exerted. THIRD, the condensers are certain vessels of my invention, in which the steam is condensed, either by immediate mixture with water sufficiently cold or by contact with other cold bodies, which condensers are situated either in that part of the cylinder itself which the steam never enters, except to be condensed or reduced to water, or they communicate with the cylinder by means of pipes, which are opened or shut at proper times, or those pipes called eduction pipes, which lead to the air pumps or other contrivance for carrying off the condensed steam, air, and water of injection, are themselves used for that purpose. FOURTH, the air and hot water pumps are pumps or other contrivances which serve to extract the air and heated water from the cylinders and condensers. FTFTH, the working beam is a double‑ended lever, a wheel or wheels, or other machinery establishing the means of communicating the power from the piston to the pump work, or other machinery to be wrought by the engine.

MY FTRST NEW IMPROVEMENT in steam or fire engines consists in admitting steam into the cylinders or steam vessels of the engine only during some certain part or portion of the descent or ascent of the piston of the said cylinder, and using the elastic forces, wherewith the said steam expands itself in proceeding to occupy larger spaces, as the acting powers on the piston through the other parts or portions of the length of the stroke of the said piston; and in applying combinations of levers, or other contrivances, to cause the unequal powers wherewith the steam acts upon the piston, to produce uniform effects in working the pumps or other machinery required to be wrought by the said engine: whereby certain large proportions of the steam hitherto found necessary to do the same work are saved. To explain which principle or improvement, I have delineated a section of a hollow cylinder at figure 1st in the annexed drawing. The said cylinder is perfectly shut at the lower end by its bottom CD, and also at the upper end by its cover AB; the solid piston EF is accurately fitted to the said cylinder, so that it may slide easily up and down, yet suffer no steam to pass by it: the said piston is suspended by a rod or rods GH, which is capable of sliding through a hole in the cover AB of the cylinder, and its circumference is made air and steam‑tight by a collar of oakum, or other proper materials, well greased, and contained in the box O; and near the top of the cylinder there is an opening J to admit steam from a boiler. The whole cylinder, or as much of it as possible, is inclosed in a case MM containing steam, or otherwise is maintained of the same heat with boiling water, or of the steam from the boiler. These things being thus situated, and the piston placed as near as may be to the top of the cylinder, let the space of the cylinder under the piston be supposed to be exhausted or emptied of air, steam, and other fiuids; and let there be a free passage above the piston for the entry of steam from the boiler, and suppose that steam to be of the same density or elastic force as the atmosphere, or able to support a column of mercury of thirty inches high in the barometer. Then I say that the pressure or elastic power of the said steam on every square inch of the area or upper side of the piston, will be nearly fourteen pounds avoirdupois weight, and that if the said power were employed to act upon the piston through the whole length of its stroke, and to work a pump or pumps, either immediately by the piston rod prolonged, or through the medium of a working beam or great lever, as is usual in steam engines, it would raise through the whole length of its stroke a column or columns of water, whose weight should be equal to ten pounds for each square inch of the area of the piston, besides overcoming all the frictions and vis inertia, of the water and the parts of the machine or engine. But supposing the whole distance from the under side of the piston to the bottom of the cylinder to be eight feet, and the passage which admitted the steam from the boiler to be perfectly shut when the piston has descended to the point K two feet, or one‑fourth of the length of the stroke or motion of the said piston, I say that when the piston had descended four feet, or one‑half of the length of the stroke, the elastic power of the steam would then be equal to seven pounds on each square inch of the area of the piston, or one‑half of the original power; and that when the piston had arrived at the point P, the power of the steam would be one‑third of the original power, or four pounds and twothirds of a pound on each square inch of the piston's area; and that when the piston had arrived at the bottom or end of its stroke, that the elastic power of the steam would be one-fourth of its original power, or three pounds and one‑half pound on each square inch of the said area. And I further say, that the elastic power of the steam at the other divisions marked in the lengths of the said cylinder, are represented by the lengths of the horizontal lines or ordinates of the curve KL, also marked or delineated in the said cylinder, and are expressed in decimal fractions of the whole original power by the numbers written opposite to the said ordinates or horizontal lines. And I also say, that the sum of all these powers is greater than f~•fty‑seven hundred parts of the original power multiplied by the length of the cylinder; whereby it appears that only one‑fourth of the steam necessary to fill the whole cylinder is employed, and that the effect produced is equal to more than one‑half of the effect which would have been produced by one whole cylinder full of steam, if it had been admitted to enter freely above the piston during the whole length of its descent; consequently that the said New or Expansive Engine is capable of easily raising columns of water whose weights are equal to five pounds on every square inch of the area of its piston, and that with onefourth of the contents of the cylinder of steam. AND BE IT REMEMBERED, though, for example's sake, I have mentioned the admission of one‑ fourth of the cylinder's fill of steam, (as being the most convenient), that any other proportion of the fill of a cylinder, or any other dimensions of the cylinder, will produce similar effects, and that in practice I actually do vary these proportions as the case requires. And also, in some cases, I admit the required quantity of steam to enter below the piston, and I pull the piston upwards by some external power against the elastic force of the steam from the boiler, which then always freely communicates with the upper part of the cylinder, and which produces similar effects to those described. But the powers which the steam exerts being unequal, and the weight of the water to be raised, or other work to be done by the engines, being supposed to resist equally throughout the whole length of the stroke, it is necessary to render the whole acting powers equal by other means.

Fig. 1

I PERFORM THIS, FIRST, by means of two wheels or sectors of circles, one of which is attached to the pump rods, and the other to the piston rod of the engine, and which are connected together by means of rods or chains, or otherwise, so that the levers whereby they act upon one another decrease and increase respectively during the ascent or descent of the piston, in, or nearly in, the ratios required. This method, mechanism, or contrivance, is delineated in fig. 2nd and also its application to one of my new invented steam engines, the sole use and benefit of which was granted to me by an Act of Parliament passed in the fifteenth year of the reign of his present Majesty. The operation of the engine with this new mechanism added to it is described as follows: The piston A being at its highest place, and the part of the cylinder under it exhausted of steam and air, the regulating valve which admits the steam to enter below the piston being shut, and the valve F which allows steam or air to pass to the condenser GK being open, in order to maintain a good vacuum, the top regulating valve D is opened, and permits the steam from the boiler to enter and act upon the piston, which then begins to descend, and to pull round the wheel or sector of a circle to which it is hung: when the point Q of that wheel has moved to R, the piston has descended two feet, and the point V of the wheel to which the pump rods or other machinery wrought by the engine are suspended, being pulled by the rod, 5, connecting it with the other wheel QRSTU, will have moved through the space VW, the regulating valve D is then shut, so that no more steam may be admitted from the boiler during that stroke, but the piston continues to descend by virtue of the expansion of the steam; and when the point Q is come to the points RSTU, the point V is come to the points WXYZ, respectively describing spaces which are nearly proportional to the powers of the steam at the corresponding points of the descent of the piston: when the piston has made its stroke and is come to the bottom of the cylinder, the regulating valve F is shut, and the valve E is opened, by which means the steam passes from the part of the cylinder above the piston to the part below it, by the pipe C, and, so restoring the equilibrium, permits the piston to ascend to its first position. The regulating valve E is then to be shut, and the exhaustion regulating valve F is opened; the steam rushes into the eduction pipe GG, where it meets a jet of cold water, which enters through the injection pipe H, which is opened immediately before the regulating valve F. The contact of this cold water immediately reduces the steam to water, and produces a vacuum under the piston, and thereby enables the elastic force of the steam to act again upon it, as has been described. Or, instead of injecting cold water into the condenser or eduction pipe itself, I bring the steam into contact with thin plates or pipes of metal, which have their external surface cooled by contact with water or other cold matter: the condensed steam, the injection water, and the air which entered with it, or any other air which has entered by other means, proceed by the eduction pipe to the air pump K, and, passing the valves of its bucket or piston, are retained and lifted up by it on the return of the stroke, and thereby are thrown into the hot water pump J, which by the next stroke raises up and delivers them into the atmosphere, from whence part is returned into the boiler to supply its consumption of water, and the remainder is conveyed away for any other purpose, or runs to waste. Another Variety of this method of equalizing the power is delineated in figure 3rd. The piston is suspended to the arch A, by means of a chain, or otherwise, and the pump rod is suspended to the arch B. The primary or cylinder arch A, by means of the arm OP, and the rod or chain OC, acts upon the working beam BC, to the arch of which the pump rods are suspended, by which means, while the piston descends through the equal spaces JK, KL, LM, MN, the pump rod is made to ascend through the unequal spaces DE, EF, FG, GH, which are nearly proportioned to the elastic forces of the steam at the respective points.

Fig. 2

MY SECOND METHOD, or piece of mechanism for equalizing the powers of the steam, is by means of chains, which are wound upon one spiral and wound off another as the piston descends, which spirals are fixed upon two wheels or sectors of circles, to which the chains of the piston and pump rods are attached: and is represented in figure 4th. The piston is suspended from the side A of the wheel AB, and the pump rods from the side C of the wheel DC, which wheel DC being pulled by the chains, J, R, K, the points of its circumference move through the unequal spaces KL, LM, MN, NO (almost exactly proportioned to the powers of the steam), while the points of the circumference of AB move through the equal spaces EF, FG, GH, HI.

MY THIRD METHOD, or piece of mechanism for equalizing the powers of the steam, is by means of a friction wheel or wheels attached to or suspended from one sector or wheel, and acting upon a curved or straight part of another sector, wheel, or working beam. Two modes of this contrivance are delineated in figures 5th and 6th, of which it is only necessary to observe that the pistons of the engines are suspended to the arches AA, and the pump rods to the arches of the working beams BB, and that these contrivances afford the means of equalizing the powers of the steam very exactly.

MY FOURTH METHOD, or piece of mechanism for equalizing the power of the steam, is by causing the centre of suspension of the working beam, or great lever, to change its place during the time of the stroke, whereby the end of the lever to which the piston is suspended becomes longer, and the end to which the pump rods are suspended becomes shorter, as the piston descends in the cylinder. An easy method of doing this is represented in figure 7th: AB represents the working beam; B, the end to which the piston is suspended; A, the end to which the pump rods are suspended; CD, a hollow curve of wood or metal fixed to the lower side of the working beam; E, the end of a friction roller, which rolls between the curve CD and the plane or support FG. This friction roller is divided into three parts, as may be seen in its horizontal view KLM: the two end parts KM, which roll upon the supports FG, are fixed firmly upon an axis; the middle part L, which rolls under the curve CD, can turn round on its axis; therefore, when by the action of the piston on the working beam the end B is pulled downwards, the roller proceeds towards C to the part of the curve which is then the highest, and thereby lengthens the lever by which the piston acts on the pumps, and shortens that by which the pumps resist the cylinder, and that in any ratios which may be required, according to the form of the curve.

Fig. 7

MY FIFTH METHOD, piece of mechanism, or contrivance for equalizing the power of the steam, consists in placing upon, suspending from, or fixing to the working beam of the steam engine, or some other beam, wheel, or lever connected with it, a quantity of heavy matter, in such a manner that the said heavy matter shall act against the power of the piston at the commencement of the descent of the said piston, and, as the piston descends, shall gradually move towards that end of the beam to which the piston is suspended, or otherwise shall act in favour of the piston in the latter part of the stroke. Three Methods or Varieties upon this principle are represented at figures 8th, 9th, and 10th. Figure 8th operates by means of a heavy cylinder A, of iron or other material, which rolls in a hollow curve BC on the back of the working beam, and will consequently change its place, and proceed towards the cylinder end of the beam, as the piston descends. In figure 9th, the same is performed by a heavy weight of iron or other matter, A, fixed above the beam or wheel, so that its centre of gravity at beginning the motion lies nearer the pump end of the beam than the centre of suspension of the beam, whereby it acts against the piston, and at last comes to be at the same side of that centre, with the end to which the piston is suspended, and thereby acts in its favour. Figure 10th shows a method of fixing the working beam itself, so as to perform in some degree the office of the weight in figure 9th. Figure 11th shows a Fourth Method, whereby I perform the same thing, by causing a quantity of water or other liquid to oppose the ascent of the piston in the beginning of the stroke, and to assist it in the latter part. A and B represent two cylinders or other formed vessels filled with water, or some other liquid, above their pistons C and D, the rods of which are fixed (or suspended) to the working beam of the engine, or such secondary or auxiliary beam as may be applied to this use, on the opposite sides of its axis. These cylinders are open at bottom and at top, and at the top part they are connected together by a lander or trough, close or open: when the piston descends, it raises the opposite end of the working beam and the piston of cylinder B, and thereby causes the water it contains to run over into A, the piston C of which, becoming loaded thereby in proportion as piston D rises, gradually comes to assist the piston of the steam vessel in the latter part of its motion. These cylinders, containing water, may be either placed below the working beam or above it, or may be suspended to a secondary working beam, constructed for that purpose, or necessary for some other use connected with the piston rod or pump rod, or other part, and placed so that the water cylinders may be out of the engine‑house, in some place where it may be found to be more convenient.

Fig. 8

Fig. 9

Fig. 10

Fig 11

MY SIXTH METHOD, piece of mechanism, or contrivance for equalizing the powers of the steam, consists in employing the surplus power of the steam upon the piston‑in the first parts of its motion, to give a proper rotative or vibratory velocity to a quantity of matter which, retaining that velocity, shall act along with the piston, and assist it in raising the columns of water in the latter part of its motion, when the powers of the steam are defective: two methods by which I perform this are delineated in the drawing of the engine, figure 12th. The heavy fly XX is put in motion by means of a pinion or smaller wheel Y fixed upon its axis, and the teeth of which pinion or smaller wheel are acted upon by the toothed sector QQ, fixed upon the arch of the working beam; or the said fly is by other means connected with the motion of the said working beam. When the piston pulls down the end of the working beam, the toothed sector QQ gives motion to the pinion, and thereby gives velocity to the fly; and when the descending or ascending velocity of the arch or sector of the working beam comes to be less than the velocity which the pinion and fly have acquired, then the velocity of the fly continuing, causes the pinion to act upon the sector in its turn, and assist the powers of the steam, until its velocity is spent, or the piston has reached the bottom of the cylinder; and the said fly operates in like manner during the ascent of the piston, but turns then in the contrary direction. In the Second Variety of this method, a fiy, or heavy wheel, is put into a continued rotative motion by a crank, by any of the rotative motions for which I have obtained his Majesty's Royal Letters Patent, dated in the present year of his reign, or by any other means which shall or can produce a continued rotative motion. And the said rotative machinery is connected with or joined to either end of the working beam, to or with the piston rod itself, to or with the pump rods, or to or with any other moving part of the engine or pump rods which is found proper. In the drawing, figure 12th, T, U, W, V, V represent the application of my Fifth Method of producing rotative motions from steam engines, as a method or contrivance for equalizing the power of the steam. The piston being at the top of the cylinder, and the working beam in the situation delineated, the engine begins its stroke, and, by means of the connecting rod TT, pulls upwards the toothed wheel W, which is fixed to the connecting rod in such manner that it cannot turn upon its own axis, and is confined by means of a link or chain reaching from its centre to the axis of the other toothed wheel U, or is otherwise contrived so that it cannot recede from it; therefore, when the action of the engine pulls the wheel W upwards, it revolves round the other wheel U, and causes it (U) to revolve upon its own axis; and the fly or heavy wheel W being fixed upon the same axis, it is also put into motion, and because of the great power of the steam in the first parts of the stroke, the fly acquires a great velocity, whereby, through the medium of the two wheels and the connecting rod, it acts upon the working beam, and assists the action of the steam in the latter parts of the stroke: when the piston has completed its stroke downwards, the lower edge of the wheel W has passed over the upper edge or highest part of the wheel U, and, the velocity of the fly continuing, the wheel U acts upon the wheel W, and assists the unbalanced weight of the pump rods in raising the piston to the top of the cylinder. BUT BE IT REMEMBERED, that I (the said JAMES WATT) do not mean that anything which I have herein set forth, touching or concerning this second variety of applying my Sixth Method or contrivance for equalizing the powers of the steam, shall be construed or thought to be intended to preclude any other person or persons from using or applying to the moving, turning, or working of mill‑work or other machinery, where continued rotative motions are required, any contrivances or inventions for producing rotative motions from steam engines, provided that such rotative motions or machinery be not of my invention, and such engines be not applied principally or solely to the raising of water: the true intent and meaning of the aforesaid last article of this writing, being to specify the means by which I apply continued rotative motions, as some of my methods or contrivances to equalize the expansive powers of the steam, in engines which are used principally or wholly for the raising of water from mines, rivers, ponds, marshes, lakes, and other places.

Fig. 12

MY SECOND IMPROVEMENT upon steam or fire engines consists in employing the elastic power of the steam to force the piston upwards, and also to press it downwards alternately by making a vacuum above or below the piston respectively, and at the same time employing the steam to act upon the piston in that end or portion of the cylinder which is not exhausted; so that an engine constructed in this manner can perform twice the quantity of work, or exert double the power in the same time, (with a cylinder of the same size), which has hitherto been done by any steam engine in which the active force of the steam is exerted upon the piston only in one direction, whether upwards or downwards. This improvement, as applied to one of the steam engines of my invention, is delineated in figure 12th. The lower part of the cylinder B being exhausted of air, steam, and other fluids, the regulating valve F being open, and the regulating valves E and N being shut, the regulating valve D is opened, which admits the steam from the boiler to press upon the upper side of the piston, by the action of which steam the piston descends, pulls down the cylinder end of the working beam, and raises the end to which the pump rods are suspended. When the piston is arrived at the bottom of the cylinder, or end of its stroke, the valve F is shut, and the valve E is opened, which admits the steam under the piston, and at the same time the valve D is shut, which prevents the steam from coming from the boiler into that end of the cylinder, and the other valve N in the upper nozzle or regulator box is opened, which permits the steam to rush from above the piston into the eduction pipe GG, where it meets the jet of injection water, which condenses it and produces a vacuum in the upper part of the cylinder, which, destroying the equilibrium, permits the steam under the piston to force it upwards. Then the piston rod being fast in the piston, and having the toothed rack OO fixed to its upper end by means of the teeth thereof, which are engaged in the teeth of the toothed sector which is fixed to or forms a part of the arch QQ of the working beam, or by means of double chains or any other practicable method, the piston or its rod raises the cylinder end of the working beam, and also a heavy weight concealed or contained in the arch thereof, or otherwise fixed, attached, or suspended thereto; which weight ought to be equal, or nearly so, to the force or power of the steam when acting upon the piston in the ascending direction. When the piston has arrived at the summit of its‑motion, the regulating valves E and N are to be shut, and the regulating valves D and F opened, whereby the piston again commences its motion downwards, as has been described; and, during the descent of the piston, the weight QQ, fixed or suspended to the working beam, assists the power of the steam on the piston, in raising the column of water in the pumps, or in working other machinery. In figure 13th is delineated a front view of the cylinder, and a section of the condenser of this engine, wherein the pipes which convey the steam from the boiler, and to the condenser, are properly distinguished and explained. This improvement permits the engine to be used either with the uniform exertion of the whole power of the steam on the piston, both in the descent and ascent; or, by making the weight of the columns of water in the pumps, or the resistance of other machinery which it may be required to work, equal to the full power of the steam upon the piston, when acting in one direction only, and the weight on the working beam equal to half that power, it may be used as a double expansive engine, and wrought in the manner I have herein set forth in the description of my First Improvement. And in such case the Fourth, Fifth, and Sixth contrivances herein described for equalizing the powers of steam, are peculiarly applicable to this mode of constructing the engine. Wherefore I have delineated the two varieties which I have described of the Sixth method as applied to this engine. AND BE IT REMEMBERED, that either or both of them may be used at the same time, though only one is strictly necessary, and that any other two or more of the aforesaid Six contrivances, or of the varieties thereof, may be applied to one engine at the same time; that is to say, such of them whose nature admits of such combination.

MY THIRD IMPROVEMENT on steam or fire engines consists in connecting together, by pipes or other proper channels of communication, the steam vessels and condensers of two or more distinct steam engines; each of which has its separate working beam and other constituent parts of a steam engine, or is otherwise so constructed that it can work pumps or other machinery which are either connected with or are independent of those wrought by the other engine; and which two engines can take their strokes alternately, or both together, as may be required. The construction of the said machine is described as followeth, and an external front view of the steam vessels or cylinders and condenser of the two engines is delineated at figure 14th of the drawings hereunto annexed: the section or side view of the two engines is not delineated, because when viewed in that direction only one of them can be seen, the other being hid by it; and the engine which could be seen would appear the same as the engine delineated in figure 2nd, or, in respect to the working beams, as the engine delineated at figure 12th; ‑ these compound or double engines admitting the application of any of the equalizing machinery which has been hereinbefore described. In figure 14th, the cylinder of the primary engine, No. 1, receives steam from the boiler by the steam pipe 8, 9, which steam enters the cylinder by a regulating valve situated at D, its piston being at the upper end of its stroke; and the part of the cylinder which is below the piston being exhausted, the elastic power of the steam presses down the piston until it arrives at the bottom or termination of its skoke: the regulating valve D is then shut, and the middle regulating valve at E is opened, which admits the steam to enter under the piston, whereby the engine is enabled to raise up the piston to the top of its stroke, where it was at the beginning: the middle regulating valve E is then shut, and the regulating valves F and P are opened: the valve F permits the steam to pass through the eduction pipe N into the perpendicular steam pipe R of the secondary engine, and to press upon its piston, under which piston there is a vacuum. The steam which is or was contained under the piston of the primary engine, No. 1, being of the same density with the atmosphere, or nearly so, will, while the piston of the secondary engine, No. 2, remains stationary, act upon it with the full power belonging to its density or elasticity, and will thereby cause it to commence its motion downwards; but as the piston of No. 2 moves downwards the density and elastic force of the steam will diminish in proportion as the spaces which it occupies are increased; so that (in case the cylinders of the two engines are of an equal capacity) when the piston of No. 2 has arrived at the bottom or lower end of its stroke the density and elastic force of the steam will be only one‑half of what they were while the piston remained at the top. Therefore, if a simple lever, wheel, or working beam, is used for this secondary engine, No. 2, the engine ought only to be loaded with a column of water, or other work, equal to half the number of pounds on each square inch which the primary engine, No. 1, is able to work with; but if the secondary engine, No. 2, is furnished with any proper conkivance for equalizing the power of the steam, it may, incase the cylinders of the two engines are of equal capacity, be made to do seven‑tenths of the work which is done by the primary engine, No. 1. When the piston of the secondary engine, No. 2, has come to the bottom of its stroke, the middle regulating valve O is opened, and the steam rushes into the condenser GK, and in its way meets the jet of injection water, which condenses it; and thereby the upper part of the cylinder of the secondary engine, and the lower part of the cylinder of the primary engine, are exhausted of steam. The piston of the secondary engine, No. 2, having then a vacuum both above it and below it, is pulled up easily by the working beam of that engine; and, there being a vacuum under the piston of the primary engine, No. 1, the steam from the boiler exerts its power upon it, and presses it down, and the other motions are repeated, as has been described. These compound engines may also be wrought in other manners, of which I shall describe one of the best. Let the eduction pipe N be supposed to be removed, and a steam pipe S, (which is delineated in red ink), be made to communicate between the perpendicular steam pipe C of the primary engine, and the top regulator box or cross pipe Q of the secondary engine; then the piston of the primary engine, No. 1, being pressed to the bottom by steam, shuts its top regulating valve D, and opens the top regulating valve Q of the secondary engine: the piston of that engine will immediately begin to descend with a decreasing power, (as has been remarked before). When the piston of the secondary engine, No. 2, has come to the bottom of its stroke, its middle regulator O is opened, whereby the steam rushes out of the cylinders of both the engines into the condenser or condensers; and, there being vacuum both above and below the pistons of both engines, the equilibrium of both is restored, and both the pistons are permitted to be raised by the unbalanced weight of the pump rods, or other weights or machinery applied for that purpose. It is proper, in this mode of application, to make a small pipe leading from the lower part of the cylinder of the primary engine to the eduction pipe, or condenser, of the secondary engine; whereby the vacuum under and above both pistons may be maintained of an equal degree of rareness or perfection. For the more clear understanding of these improvements and contrivances I have delineated them on the parchments hereunto annexed, according to scales specified on the respective drawings, and have adapted them all, except figure 1st, to engines whose cylinders are thirty inches in diameter, and the whole length of the skoke of whose pistons is eight feet; but I make the cylinders larger or lesser, longer or shorter, and vary the proportions and shape of them and of the other parts, according as their uses may require; and as each improvement, method, piece of mechanism, or contrivance, admits of numberless variations, I have set forth and delineated only such as I esteem to be among the best, and which are the most easy to be executed.

MY FOURTH NEW IMPROVEMENT on steam or fire engines consists in applying a certain mechanical contrivance, called a toothed rack and sector of a circle, or toothed racks and toothed sectors of circles, for suspending or connecting the pump rods or pistons with the working beams, levers, or other machinery used in place of them, in place or instead of chains, which have hitherto been used for these purposes. This new improvement, or mechanical contrivance, is delineated at OQ, figure 12th, and requires no other explanation than to say that it is delineated by a scale of one‑ fourth of an inch to each foot of the real size, according to its proper dimensions for a cylinder thirty inches in diameter; and the said rack and sector are supposed to be made of hammered or cast iron, but it may be made of wood or other materials by giving it dimensions suitable to the strength of the material of which it is made; and, in order to accommodate the same to cylinders of other sizes, the strength of its parts must be increased or diminished, in proportion to the powers of the respective cylinders to which it may be applied. I have described and delineated all my aforesaid new improvements upon, and new mechanical conkivance applicable to steam engines, as applied to or connected with the new steam engines of my own invention, as being the most perfect hitherto made; but IT MUST BE REMEMBERED, that Ido apply the same to the common steam engines known by the name of Newcomen's Steam or Fire Engines; and that they are also applicable to any other species or variety of steam engines which works with a piston moving in a cylinder or steam vessel; and that they will in such engines produce greater or lesser effects in proportion to the degree of perfection of the engine to which they are applied. It is also to be remarked, and though I have described all the engines standing erect, and having the piston rods coming through holes in the top of the cylinder, that the same or nearly the same effects will be produced, though the piston rods come through holes in the bottom of the cylinder, and the working beams or equalizing machinery be placed under them; or although the cylinders and working beams are placed inclined or horizontally; and that, in certain cases, I use them in such different positions.

MY FIFTH NEW IMPROVEMENT on steam or fire engines consists in making the steam vessels in the form of hollow cylinders, or in the form of other regular round hollow vessels, or in the form of greater or lesser segments or sectors of such bodies or vessels. And I place in the centre or axis of the circular curvature of such vessels, a round shaft or axle, passing through and extending beyond one or both ends of such steam vessel; and I shut up the ends of the said steam vessel with smooth plates, which have proper apertures for the said axle or shaft to pass through; and within the said steam vessel I fix to the said axle a piston or plate, extending from the said axle to the circular circumference of the steam vessel, and also extending from one end of the steam vessel to the other. And I make the said piston steam‑tight, by surrounding the parts which fit to the steam vessel with hemp, or other soft substances, soaked in grease, oil, or wax, or by means of springs made of steel, or other solid and elastic or pliable materials; and to the said steam vessel I fix one or more plates or divisions, extending from the axle to the circumference of the steam vessel; and, where these plates or divisions join to or approach the axle, or where the said axis passes through the end plates of the steam vessel, I make such joinings steam and air‑tight, by the means above recited. In the steam vessel, on each side of the said piston, I make one or more channels or apertures for receiving and discharging the steam, which channels I furnish with proper valves for that purpose: I also apply to the said engine proper condensers and air pumps; and the pumps which raise water, or such other machinery as is required to be wrought by the said engine, are put in motion or worked by a wheel or wheels fixed to or upon the external parts of the said axle, or by any other mechanism which may be suitable. And the said engine, so constructed, is wrought by admitting the steam between the fixed division and the moveable piston, and exhausting or making a vacuum on the other side of the said piston, which accordingly, by the force of the steam, moves into the said vacuum, and turns the axle a greater or lesser portion of a circle, according to the structure of the machine. The piston is returned to its former situation by admitting steam on the other side of the said piston, and drawing the piston back by some external power, or by exhausting the part of the steam vessel which was first filled with steam. An engine constructed upon this principle is delineated at figures 15th, 16th, and 17th in the annexed drawing, according to a scale of one‑fourth of an inch to each foot of the real size; but I make them greater or lesser, and vary the shape and size of the steam vessel and other parts, according to their use. The operation of the engine is as follows: The steam vessel AAA being exhausted of steam and air, and the regulating valves K and J being shut, and L and H open, the steam coming from the boiler through the pipe M enters the steam vessel by L and G, and causes the piston C to turn round into or towards the exhausted part of the steam vessel AX, and thereby turns the axle B, and the machinery attached to it, until the piston C comes to X: the regulating valves L and H are then shut, and K and J are opened: the steam which had entered by the pipe G, and had acted upon the piston, returns through G and J into the condenser or eduction pipe O, where it is condensed; and the steam from the boiler, entering through K and F, forces the piston C to return to its first situation. The pump rods UW, or other machinery, are wrought by the wheel SS fixed on the axle BB, or otherwise, (see figures 16th and 17th); and the condenser pump (or pumps) is wrought by the wheel Q, fixed to any part of the said axle, or otherwise. It is to be understood that the said steam vessel is to be firmly fixed, so that it cannot move; and that the godgeons or pivots of the said axle must be rested upon proper supports, which things could not be exhibited in the drawing without confusion. I also cause engines, made according to this Fifth improvement, to revolve with a continued rotative motion, by making their steam vessels complete cylinders, or other circular figures; and, in place of the fixed division or divisions, I place one or more valves in their steam vessels, which shut or close the area between their axles and their circumferences, and which valves open by turning upon a hinge or joint, or are drawn back by a sliding motion like a drawer, or otherwise are constructed so that they may be removed when the piston comes to them, and thereby suffer it to pass by the place where they were, (see the drawing, figure 18th), and so begin a new revolution in the same direction; or I make a fixed division, or divisions, as has been described, and I fix one or more valves to the axle, which valves are capable of folding down, and of applying themselves to the axle, and of forming a part of its circumference, so that they can thereby pass by the division; and, when they have passed it, they are raised up by springs, or otherwise, so as to perform the office of a piston or pistons. I have not described the boilers which supply any or all of these engines with steam, because I use such as are commonly applied to other steam engines, or any kind of boiler which is capable of producing steam in sufficient quantities. Neither have I described the machinery which opens and shuts the regulating valves, asit is similar to that which is in common use, and may be varied at pleasure.

Figs. 15, 16, 17

IN WITNESS whereof I have hereunto set my hand and seal this third day of July, in the year of our Lord one thousand seven hundred and eighty‑two.

JAMBE WATT.

Sealed and delivered, being first duly stamped, in the presence of

JOHN SOUTHERN.

PETER CAPPER.

Acknowledged by the said James Watt, party hereto, the third day of July, one thousand seven hundred and eighty‑two, before me,

GEO. HOLEINGTON BARKER,

A Master in Chancery Extraordinary.

INROLLED in His Majesty's High Court of Chancery, the fourth day of July, in the year of our Lord 1782, being first duly stamped according to the tenor of the Statutes made in the sixth year of the reign of their late Majesties King William and Queen Mary, and in the seventeenth year of the reign of His Majesty King George the Third.

JOHN MITFORD. 4.P.Y.

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29. 1784 Specification of Patent

This patent was granted on 28 April 1784 and the specification was enrolled on 24 August 1784. It includes a number of improvements, of major and minor sign)ficance: (i) another steam wheel; (ii) various mechanisms, including the parallel motion, for connecting the piston‑rod to the beam, (iii) various methods of balancing pump‑rods; (iv) new methods of applying steam power to rolling and slitting mills, (v) steam‑powered forge hammers; (vi) improved method of opening and dosing regulating valves; (vii) application of steam engines 'to give motion to wheel carriages', i.e. steam locomotives. Of these inventions, the one of most immediate practical significance was the parallel motion, for connecting the piston rod of the double‑acting engine to the beam, so as to permit 'push' as well as 'pull'. The application of the steam engine to rolling and slitting mills and to forge hammers soon had important effects in ironworks, such as those of John Wilkinson. Steam locomotion, of course, was ultimately to be of the most revolutionary importance, but though William Murdock, Boulton and Watt's engine‑erector and foreman, produced a model steam carriage about this time, he was given no encouragement by Watt, who apparently patented this idea only to forestall other possible projectors.

SPEC'F'CATION OF PATENT, APR'L 28TH, 1784, FOR CERTAIN NEW IMPROVMENTS UPON FIRE AND STEAM ENG'NES, AND UPON MACH'NES WORKED OR MOVED BY THE SAME.

To ALL TO WHOM these presents shall come, I, JAMES WATT, of Birmingham, in the county of Warwick, Engineer, send greeting.

WHEREAS His Most Excellent Majesty King George the Third, by His Letters Patent bearing date at Westminster, the twenty‑eighth day of April, in the twenty‑fourth year of his reign, did give and grant unto me, the said JAMES WATT, his especial licensee, full power, sole privilege, and authority, that I, the said JAMES WATT, my executors, administrators, and assigns, should, and lawfully might, during the term of years therein expressed, make, use, exercise, and vend, within that part of his Majesty's Kingdom of Great Britain called England, his Dominion of Wales, and Town of Berwick upon Tweed, my Invention of CERTAIN NEW IMPROVEMBNTS UPON FIRE AND STEAM ENGINES AND UPON MACHINES WORKED OR MOVED BY THE SAME; in which said recited Letters Patent is contained a Proviso obliging me, the said JAMES WATT, by writing under my hand and seal, to cause a particular description of the nature of the said invention, and in what manner the same is to be performed, to be inrolled in His Majesty's High Court of Chancery within four calendar months after the date of the said recited Letters Patent, as in and by the said recited Letters Patent, and the Statute in that behalf made, relation being "hereunto had, may more at large appear.

Now KNOW YE, That in compliance with the said Proviso, and in pursuance of the said Statute, I the said JAMES WATT do hereby declare, that the nature of my said invention, and in what manner the same is to be performed, is particularly described and ascertained as follows, that is to say:

MY FIRST NEW IMPROVEMENT on steam and fire engines consists in making the steam vessel so as to be capable of turning round on pivots or on an axis, either in a vertical or horizontal direction, and in employing the elastic power of the steam to press upon the surface of any dense fluid or liquid contained in the steam vessel, and to force it to pass out at a hole or holes made in the circumference or external part of the steam vessel, in such manner that the fluid or liquid shall issue out in a line forming a tangent to the circle described by the rotation of that part of the steam vessel where the hole is situated, or at least in a line approaching to such tangent, which fluid or liquid, by its action on the fluid or liquid in which the steam vessel is immersed, causes the engine to turn round; and I replace the fluid so issuing, by immersing the steam vessel into another vessel filled with the same fluid, and by dividing it into two or more divisions or chambers, in the direction of its axis of rotation; which chambers are furnished with valves in their bottom or sides, which admit the fluid to enter into one of them, while by the force of the steam it issues from an other, and the steam is admitted into these chambers, and its action is suspended alternately by proper valves and regulators, which are opened and shut by the rotation of the machine. The machine may be made in various forms: I have delineated one of the most commodious in figure 1st of the annexed drawing, where ABCDE represents a section of the steam vessel mounted on a vertical axis, with one perpendicular partition; F, G, two valves in its bottom, to admit the surrounding liquid; H, the place of one of the holes at which it issues; J, the pivot on which it turns; K, a collar which is fitted exactly to the neck of the steam vessel, so as to be steam‑tight, and yet to give liberty to the vessel to turn round in it freely; L, a pipe conveying steam from a boiler to the steam vessel, and which is joined to the collar. There are two holes in the neck of the steam vessel which communicate with its two chambers, and, as the vessel turns round, present themselves alternately to the opening of the steam pipe within the collar, and to an opening on the opposite side of the collar, which communicates with the empty part of the vessel MN, which contains the liquid in which the steam vessel is immersed. The vessel MN is made of a cylindric or other form, and contains a quantity of quicksilver, water, oil, or other fluid or liquid, of a depth sufficient to give a resistance to the issuing fluid proportioned to the effect wanted to be produced, and to cause the fluid to fill the empty chamber of the steam vessel in proper time. If the machine is required to act only by such steam as has a greater expansive force than the pressure of the atmosphere, this vessel MN is opened at top, and the steam which has done its office is then discharged into the open air; but when the steam is required to act with the pressure of the atmosphere, in addition to its own elastic force, then the vessel MN must be shut at top, and made everywhere air‑tight, and the steam be made to pass from it by the pipe O into another vessel, called a condenser, where it is condensed by the application of cold water, or other cold bodies, by which means a vacuum is obtained, and the power of the steam is augmented. Figure 2nd is a ground plan of the steam vessel, and of the external vessel; HH are two apertures at which the fluid alternately issues, and FG are the valves by which it enters. Figure 3rd is a horizontal section of the collar and of the neck of the steam vessel, in which RR are the two apertures which admit and discharge the steam, and L the steam pipe coming from the boiler. The action of the machine is as follows: Steam being admitted into one of the chambers, causes the fluid contained in it to issue with violence at the lower aper ture belonging to that chamber, and the fluid so issuing, by its action against the quiescent fluid contained in the outer vessel, causes the steam vessel to turn round; by which means the upper aperture of the other chamber is presented to the steam pipe, and the action on the fluid in that chamber commences; at the same time the steam issues at the upper aperture of the frst chamber, anditis replenished by the fluid entering by the valve at the bottom. The machinery to be worked by the engine is put in motion by being attached, ftxed to, or connected with the end of the axis P, which passes through a hole or collar in the cover of the outer vessel MN. This engine is delineated by a scale of one inch for each foot of the real size, but may be larger or lesser, and its proportions varied at pleasure.

Figs. 1 – 3

MY SECOND NEW IMPROVEMENT on the steam engines consists in methods of directing the piston rods, the pump rods, and other parts of these engines, so as to move in perpendicular or other straight or right lines without using the great chains and arches commonly fixed to the working beams of the engines for that purpose, and so as to enable the engine to act on the working beams or great levers, both by pushing end by drawing; or both in the ascent and descent of their pistons. I EXECUTE THIS ON THREE PRINCIPLES:

THB FIRST PRINCIPLE is delineated in figure 4th, and is performed by connecting with the top of the piston rod A by means of joints, two secondary levers or beams BC, the other ends of which are furnished with arches DE, which roll upon the walls of the house FG, or on pieces of timber or other proper resisting bodies fixed at convenient distances parallel to the line of motion of the rod which is required to receive the right‑lined or perpendicular motion; and these arches are suspended in their places by means of leather belts, chains, or jointed bars of iron, attached to them. The top of the piston or pump rod, and the working beam, are also connected together by means of a piece of iron or wood H, having a joint at each end, on which it can move freely and accommodate itself both to the angular motion of the working beam JJ and to the perpendicular motion of the piston or pump rod.

Fig. 4

THE SECOND PRINCIPLE by which I produce a right-lined motion from an angular or circular motion is delineated in figures 5th and 6th, and consists in guiding the top of the piston rod or pump rod perpendicularly by means of a piece of wood or iron, or other material A, sliding in a groove made in an upright B, firmly ftxed to some part of the machine, so as to be higher than the working beam C, and in the direction of the required motion, and by connecting the end of the working beam with the top of the piston rod or pump rod D, or with the said sliding piece A, by means of a bar or bars of wood or iron E, having joints at each end. Figure 6th shows an end view of the working beam, piston rod, sliding piece, and connecting bars; and the pricked circular and angular lines, figure 5th, show the quantity of angular motion of the working beam. In figure 6th is delineated another method of using this principle: AA is the piston of the engine, which has a hollow piston rod BB, and the connecting bar CC is attached to the bottom of that hollow rod by means of a joint and to the working beam by means of another joint, and the hollow piston rod, by sliding in the collar DD, serves to direct the motion, and the hollow rod is made wide enough to permit an angular motion of the connecting bar, proportioned to the versed sine of the angle described by the working beam.

Figs 5- 6

THE THIRD PRINCIPLE upon which I derive a perpendicular or right-lined motion from a circular or angular motion consists in forming certain combinations of levers moving upon centres, wherein the deviation from straight lines of the moving end of some of these levers is compensated by similar deviations, but in the opposite directions, of one end of other levers. In figures 7th and 8th is delineated one Method of putting this principle into practice: AA represents the working beam of the engine; B, the wall or support on which it rests; CC, the spring beam; DE, a lever or bar of iron, moveable about the axis or centre D, (which is fixed to the spring beam), and also about the axis or centre E, which is connected with, or is a part of, the bar or rod EF. The bar EF is capable of sliding towards or from the axis or centre of the working beam by a sliding motion between a pair of cheeks at E, and by a portion of a circular motion of the end F round the centre H, from which it is suspended by the coupling bars or links HF. The piston rod or pump rod G is fastened to the bar FE and to the link HF by the joint pin at F. The right line FL is that in which the piston rod or its end F moves upwards and downwards. KM is a portion of a circle described from the centre of the working beam to which LF is a tangent, and KL and MF show its greatest deviations from the straight line or tangent. ENJ is a portion of a circle described on the centre D by the joint pin E, and the length of DE and the situation of the centre D are such that the lines JL, NO, EF, are equal, and are represented by the rod EF; therefore, whenever the working beam is moved on its centre, the cheeks at E and the joint at F oblige the bar EF to move upwards or downwards along with it. But the centre D being fixed, the end E of the rod ED can only move in the circle ENJ, and the joint pin E obliges the rod EF to slide under the working beam between the cheeks, and to come nearer to the centre or to recede from it, according to the position of the working beam. And as the distances between every point of the arc JNE and the corresponding points of the line LOF are always equal, the point or joint F, together with the top of the piston rod, must move in the straight line LOF. In figure 8th is delineated a view of the underside of the working beam, seen from below, in which it is shown that the bar ED is made double, in order that one part may go on each side of the working beam, and that the joint pins E, D, and F, reach from side to side of the beam. Though the apparatus is in these drawings placed below the working beam, and that beam is fixed above its own axis or godgeon, yet the contrivance will answer equally well if the whole were reversed, or if the rod EF and the axis of the working beam were placed in the middle of its depth by making the beam double. The proportions of the lengths and thicknesses of the parts to one another are such as answer in practice, but may be considerably varied, provided the principle be attended to.

Figs. 7 -8

In figures 9th, 10th, and 11th, I have delineated another Method, whereby I carry this third principle into practice. AA represents the working beam of an engine; BD, the piston rod or pump rod; CDE, one of two bars of iron or wood, connected, by joints at E and D, with the working beam and with the top of the piston rod respectively, and at C, by a joint, to an angling bar or bars CF, the other end or ends of which is or are connected with the wall of the house, or some firm support, by a joint or joints at F, on which, as a centre, the bar CF is moveable. When the working beam is put in motion on its axis, the point E describes the arc HEJ, and the point C describes the arc KCL on the centre F, and the convexities of these arcs, lying in opposite directions, compensate for each other's variations from a straight line; so that the joint D at the top of the piston rod or pump rod, which lies between these convexities, ascends and descends in a perpendicular or straight line. The respective lengths of the radii GE and CF and their proportions to one another may be varied, but if the radius CF be lengthened more in proportion than GE, the point D must be placed proportionably further from E and nearer to C, and vice versa, as is pointed out by geometry. The regulating radius or rod CF may also be placed above the working beam, and the latter may be reversed in regard to its own axis, where such construction is found more convenient. In figure 10th I have delineated a horizontal view of the radii CF, and in figure 11th an end view of the working beam A and the connecting bars EDC with the piston rod BB.

Figs. 9 - 11

In figure 12th I have delineated another Method, whereby I put this third principle into practice. The regulating radius FH being centred at H on a firm support, and the connecting bar FBG being connected with the working beam by a joint at B, is prolonged to G, where it is connected with the piston rod or pump rod GC by another joint. As the radius FH is shorter than the radius JB, the parts of the connecting rod FB, BG are so proportioned to one another, that on account of the difference of the convexities of the arches FE and BC, the point G and the piston rod GC will always ascend and descend in a perpendicular or straight line. This machinery also admits of being reversed; that is, the regulating radius HF may be placed under the working beam, and the working beam above its own centre of motion, in cases where that is found more convenient. This third principle may also be put in practice by other methods, but those delineated are in general the most eligible: all of them are laid down by a scale of one‑fourth of an inch for each foot of the real size, in their proper proportions for engines whose cylinders are twenty inches in diameter, and the length of whose stroke is four feet; except figures 5th and 6th, which are delineated for a six feet stroke; and figure 19th, which is laid down for a cylinder fifteen inches in diameter and twelve inches length of stroke; but all the dimensions admit of considerable variation, according to the exigency of the case, and, preserving the proportions, are applied to cylinders of different diameters and lengths of stroke.

MY THIRD NEW IMPROVEMENT is upon the application of steam or fire engines to work pumps or other alternating machinery. It consists in causing, by proper machinery, one half or one part of the pump rods to ascend while the other descends, whereby the weight of the pump rods, and other moving parts, always nearly balance one another, and the necessity of employing other matters to balance their weights, which are frequently enormous, is avoided. It is particularly applicable to engines which act forcibly both by the ascent and descent of the piston in the cylinder, but may also be advantageously employed to engines which act forcibly by the motion of the piston in one direction, as in such cases the weight of one set of pump rods may be employed, during their descent, to pull up the rods of other pumps, and thereby to work them: I PERFORM THIS IN VARIOUS METHODS, of which I have delineated two of the best.

THE FIRST OF THESE consists in suspending one‑half, or part of the pump rods, to one end of a lever or working beam; and the other part, or half, to the other end of the same lever, which lever or working beam is supported on a centre or axis in some part of its length between the two rods, and the said rods are connected with or suspended to or from the said double lever by means of simple joints or by means of chains and arches, or, in place of a lever, a wheel and chain may be used. The said lever may either be the working beam of the engine, or a separate lever placed over, or within, the mouth of the pit or shaft, and receiving its motion either directly from the piston rod of the engine, or from the working beam by means of a stiff rod; or, in case of the engine being of that kind which acts only in one direction, by means of a chain or rope. In figure 13th, AA represents the double lever; B, its centre or axis; CL and DM, two rods of wood or iron, or two chains connecting this beam with the pump rods, which pump rods are suspended to the joints ML. KK represent two wheels which serve to guide the rods, and to bring them nearer together than they would naturally hang, in cases where the connecting rods CL, DM cannot be admitted to hang perpendicularly under the ends of the double lever; and J represents the lower end of a stiff rod, reaching from the working beam, or other moving part of the engine, and connected with the double lever AA by means of the joint H. and be it remarked, that in cases where the connecting rods CL, DM are kept from their perpendicular position by means of wheels, (such as KK), the lower ends ML of these rods would describe curved or angular lines, which would disturb the perpendicularity of the pump rods suspended from these points. In order, therefore, to avoid such defect, I form the lower part of these connecting rods into curves, as shown in the drawing, which curves, acting against the wheels KK, compensate for the irregularities which would otherwise take place, and cause the points L and M, and the pump rods which are attached to them, to ascend and descend in perpendicular lines: (the figure of such curve is readily found by geometry).

Fig. 13

THE SECOND METHOD consists in connecting together levers which turn or move on separate or different axes or centres, in such a manner, that the moveable end of one lever shall descend when the moveable end of the other lever ascends, and vice versa; and in connecting the moveable end of one of these levers with the working beam or piston of the engine in some proper manner, and in suspending the pump rods to the moveable ends of these levers by means of joints or chains. NO. 14 represents a combination of levers which comes under that description. The two similar frames BFEH and CGDJ, are moveable on their respective centres E and D, and are connected together by a brace or braces HKJ, SO that the pieces HE and JD must, when put in motion, continue parallel to one another; and consequently, from the positions of the pieces or levers F and G, when the joint pin B describes the arc BN, the joint pin C of the other frame must describe the arc CO in the opposite direction, by which means the pump rod L ascends when the pump rod M descends, and vice versa; and these frames are connected with the engine, or its working beam, by means of the rod or chain AB; or in place thereof, one of the levers F or G is prolonged on the other side of their respective centres E or D to a suff~•cient length to become itself the working beam of the engine. And the whole of this machinery may be reversed or placed upside down: that is, the levers EH and DJ, with the brace or braces HKJ, may be placed above their centres E and D instead of being placed below them, and may also upon the same principle be varied in other manners. The machinery delineated in figures 13th and 14th is laid down by a scale of one‑fourth of an inch for every foot of the real dimensions, and is adapted for cylinders of twenty inches diameter and four feet stroke; but machinery on the same principles is made for larger or lesser engines, as required.

Fig. 14

MY FOURTH NEW IMPROVEMENT consists in new methods of applying the power of steam engines to move mills for rolling and slitting iron and other metals, or to move other mills which have many wheels which are required to turn round in concert, so that the same steam or fire engine shall directly, by means of a double working beam, or by means of a strong piece of wood or other material fixed across one end of the working beam, and by means of two separate rods connecting the said working beam or cross beam with proper machinery for producing rotative motions, give motion to two primary wheels fixed either on the same or separate axes, whether acting in concert or applied to different uses; and in connecting together, by means of a secondary axis carrying two or more wheels, different primary motions produced by the same engine, or by two or more different engines, which methods are particularly applicable to the connecting together the motions of the rollers and slitters, or of different pairs of rollers, in mills for rolling and slitting metals, which are worked by fire or steam engines. In figures 15th, 16th, and 17th is delineated the application of this improvement to a slitting mill, which drawings exhibit that machine in three different views, in all of which the same parts are marked with the same letters. Figure 16th is a section of the mill through the line XX of figure 17th, except in what relates to the working beam AB, the cross beam C, and the upper ends DE of the two connecting rods of the rotative motions. In order to avoid confusion, the rod E is represented as broken off, and the remaining part of it and the position of the rotative motion which it works are represented by the red ink dines and circles Q and R. F is the revolving wheel of a rotative motion, which is fixed to the rod D, and GG is the centre wheel of the same motion, which is fixed upon the axis of the fly wheel JJ and of the toothed wheel KK, to both which it gives motion, and also to the lower set of the slitters which are turned by that axis. The toothed wheel KK acts upon and gives motion to another toothed wheel NN, which is fixed on the same axis with the fly wheel OO, which turns the upper roller in the roll frame P, and the direction of the motion of these and the other wheels is shown by the darts. And the rod E, with the rotative motion QR, (figures 15th and 17th), turns the fly wheel MM, and the toothed wheel LL, which is upon the same axis with that fly, and which axis also turns the upper set of the slitters. The toothed wheel LL acts upon and turns the toothed wheel SS and its fly wheel TT, and their axis turns the lower roller. The motion is thus communicated to all the wheels and flys, and also to both the rollers and slitters. But as the flys JJ and TT must turn in the opposite direction to the flys MM and OO, and as there is nothing in the rotative motions themselves that can determine these wheels to take contrary motions at first setting out, and as the top and bottom of the motion of the connecting rods D and E, and the revolving wheels which are fixed to them, the necessary shake in the teeth of the wheels of the rotative motions will permit the fly wheels on one side of the mill to run faster than those on the other, which produces a very prejudicial effect on the whole machine, I have contrived to connect the toothed wheels KK and SS together, by means of the toothed wheels V and W, fixed on the secondary axis Y under the other machinery: the teeth of the wheel V are engaged into the teeth of the wheel K, and the teeth of the wheel W are engaged into those of the wheel S; so that W and V being on the same axis, cause K and S to turn in the same direction, and consequently L and N to turn in the contrary direction, and the whole wheels to move in an uniform manner. In place of the cross beam C, two working beams may be used, united together at the ends which are next the cylinder, and opening to the proper distance at the other ends like the letter V, and one of the connecting rods may be suspenW to one of these beams, and the other rod to the other beam. In other cases, where the power required is not very great, I construct slitting mills with engines which have only one working beam and one set of machinery for producing a rotative motion, which is connected with the axis of one of the fly wheels, from whence the motion is transmitted to the other parts of the machines by the toothed wheels KK, LL, NN, and SS, and by the secondary axis Y and its toothed wheels V and W. The whole of this machinery is drawn in its due proportions, to a scale of one‑fourth of an inch to each foot of the real size, to be moved by an engine with a cylinder of forty‑eight inches diameter and six feet length of stroke, but it is made larger or lesser, as required.

Fig. 15

Fig 16

Fig. 17

BE IT REMEMBBRED, that although in order to explain my said Fourth new improvement, I have been obliged to delineate the whole of a slitting mill, yet that the new improvements which are the subjects of this article of the Specification, are only, the communicating the motion from the same steam or fire engines to two separate primary axes or shafts and sets of wheels moving in the same or in contrary directions; and in connecting together four or more sets of wheels by means of secondary axes or shafts carrying two or more wheels each, such as the shaft or axis Y and its wheels V and W; both which improvements are, to the best of my knowledge, entirely new. In figure 2Oth I have delineated the machinery by which the rotative motion is in this case proposed to be communicated from the working beam of the engine to the millwork, (which is one of the methods described in the Specification of certain Letters Patent which his present Majesty was most graciously pleased to grant to me, bearing date the twenty‑fifth of October, in the twenty‑second year of his reign). But this drawing is only intended for elucidation, for I apply to this purpose not only the rotative machinery now delineated, but also any other kind which is proper or suits the particular case.

MY F1PTH NEW IMPROVEMENT consists in applying the power of steam or fire engines to the moving of heavy hammers or stampers, for forging or stamping iron, copper, and other metals or matters, without the intervention of rotative motions or wheels, by fixing the hammer or stamper, to be so worked, either directly to the piston or piston rod of the engine, or upon or to the working beam of the engine, or by fixing the hammer or stamper upon a secondary lever or helve, and connecting the said lever or helve by means of a strap, or of a strong rod, to or with the working beam of the engine, or to or with its piston or piston rod. In figure 18th is delineated, on a scale of one‑third of an inch for each foot of the real size, a view of an engine of my invention, with a cylinder of fifteen inches diameter, working a hammer of five hundred pounds weight: in which, A is the cylinder; B, the piston rod; CC, the working beam of the engine; DD, the drom beam of the forge, which in this case is made double; E, a strong post, which carries the end of the drom beam; F, the rabbit or spring piece which regulates the ascent of the hammer and beats it back; GG, one of the two legs which carry the axis of the hammer; H, the hurst or axis of the hammer helve; J, the helve; K, the puppet or piece which supports the rabbit; L, the hammer; N, the anvil, and M, the rod which connects the helve with the working beam; OP, the nozzles or regulator boxes; R, the condensing vessel; S, the condenser pump; TT, a cistern of cold water; V, the plug frame which opens and shuts the regulators; and W, a steam pipe coming from a boiler.

Fig. 18

In figure 19th is delineated, on a larger scale, a section of the cylinder, and a view of the apparatus by which, in cases where the engines are required to be worked very quick, the regulators are opened and shut; which shall be described in the next section.

Fig. 19

MY SIXTH NEW IMPROVEMENT consists in making the regulating valves which admit the steam into the cylinders of fire or steam engines, or which suffer it to go out of them, in such manner that they are pushed open by the action of the steam upon them, and are kept shut by certain catches or detents, which are unlocked at proper times, either by hand or by the engine itself. I perform this by making the circumference of these valves in a conical or tapering form, as shown at P and Q, figure 19th; and by grinding or otherwise fitting exactly the said circumferences to a ring of metal which is called the valve seat, so that when shut it may be steam or air‑tight: the valves Q and P are suspended or supported by links or by racks and sectors which connect them with certain levers E and F in the insides of the nozzles, which, by means of the spindles or axes on which they are fixed, communicate with the levers G& which are upon the outside of the nozzles, and are connected by the rods HH with the short levers ST and VW turning upon their respective axes S and V. When the valve is shut, the centres of the pins T and W lie a little beyond the straight lines, passing through the centres of S and G and of V and G, and no force applied at GG can unlock or discharge the valves P and Q until the points T and W are moved to the other sides of the straight lines SG and VG respectively. When the piston of the engine descends, the valve P is shut and Q is open; the pin X strikes the handle K, which shuts Q, and the pin M immediately strikes the handle J, which, moving the point T from the right line, disengages the valve P, and suffers it to open. The piston AA then ascends with the plug tree L, and the pin Z returns the handle J to its proper position, which shuts P, and the pin N strikes the handle K, which permits Q to open, and the piston AA descends into its first position and commences a new stroke upward, and so continuedly. And the power and velocity of the engine is regulated by opening or shutting a regulating valve placed at 0, which admits more or less steam, as required.

MY SEVENTH NEWIMPROVEMENT is upon steam engines which are applied to give motion to wheel carriages for removing persons or goods, or other matters, from place to place, and in which cases the engines themselves must be portable. Therefore, for the sake of lightness, I make the outside of the boiler of wood, or of thin metal, strongly secured by hoops, or otherwise, to prevent it from bursting by the strength of the steaTn; and the fire is contained in a vessel of metal within the boiler, and surrounded entirely by the water to be heated, except at the apertures destined to admit air to the fire, to put in the fuel, and to let out the smoke; which latter two apertures may either be situated opposite to one another in the sides of the boiler, or otherwise, as is found convenient; and the aperture to admit air to the fire may be under the boiler. The form of the boiler is not very essential, but a cylindric or globular form is best calculated to give strength. I use cylindrical steam vessels with pistons, as usual in other steam engines, and I employ the elastic force of steam to give motion to these pistons, and after it has performed its office I discharge it into the atmosphere by a proper regulating valve, or I discharge it into a condensing vessel made air‑tight and formed of thin plates or pipes of metal, having their outsides exposed to the wind, or to an art)ficial current of air produced by a pair of bellows, or by some similar machine wrought by the engine or by the motion of the carriage; which vessel, by cooling and condensing part of the steam, does partly exhaust the steam vessel, and thereby adds to the power of the engine, and also serves to save part of the water of which the steam was composed, and which would otherwise be lost. In some cases I apply to this use engines with two cylinders which act alternately; and in other cases I apply those engines of my invention which act forcibly both in the ascent and descent of their pistons, and by means of the rotative motion in figure 20th, or of any other proper rotative motion, I communicate the power of these engines to the axis or axletree of one or more of the wheels of the carriage, or to another axis connected with the axletree of the carriage by means of toothed wheels; and in order to give more power to the engine when bad roads or steep ascents require it, I fix upon the axletree of the carriage two or more toothed wheels of different diameters, which when at liberty can turn round freely on the said axletree when it is at rest, or remain without turning when it is in motion; but, by means of catches, one of these wheels at a time can be so fixed to the axletree, that the axletree must obey the motion of the toothed wheel, which is so locked to it. And upon the primary axis, which is immediately moved by the engine, or which communicates the motion of the engine to the axletree of the carriage, I fix two or more toothed wheels of greater or lesser diameters than those on the axletree, which are moved by them respectively, so that the wheels on these two axles having their teeth always engaged in one another, the wheels on the axle of the carriage always move with the wheels on the axle of the rotative motion, but have no action to turn the wheels of the carriage except one of them be locked fast to its axletree, ‑ then the latter receives a motion faster or slower than that of the axle of the rotative machinery, according to the respective diameter of the wheels which act upon one another. In other cases, instead of the circulating rotative machinery, I employ toothed racks or sectors of circles worked with reciprocating motions by the engines, and acting upon ratchet wheels fixed on the axles of the carriage. And I steer the carriage, or direct its motion, by altering the angle of inclination of its fore and hind wheels to one another by means of a lever or other machine. As carriages are of many sizes and variously loaded, the engines must be made powerful in proportion. But to drive a carriage containing two persons, will require an engine with a cylinder seven inches in diameter, making sixty strokes per minute of one foot long each, and so constructed as to act both in the ascent and descent of the piston; and the elastic force of the steam in the boiler must occasionally be equal to the supporting a pillar of mercury thirty inches high.

Fig. 20

LASTLY, as throughout this Specification I have particularly described my several new Improvements as applied to the improved steam engines of my invention, the sole use and property of which his present Majesty was most graciously pleased to grant to me, my executors, administrators, and assigns, by his Royal Letters Patent, bearing date the fifth day of January, in the ninth year of his reign; and which were confirmed by an Act of Parliament made and passed in the fifteenth year of his reign; and for sundry improvements on which, his Majesty was also most graciously pleased to grant to me his Royal Letters Patent, bearing dates on the twenty‑fifth of October and the twelfth day of March, both in the twenty‑second year of his reign;—BE IT THEREPORE REMARKBD, the said new improvements herein particularly described are all, or most of them, not only applicable to the improved engines of my invention, but also to engines of other constructions which would be improved thereby; and that, as I suppose the Specifications of explanation of any particulars relative to my former inventions, which may not be clearly understood from these presents.

IN WITNESS whereof, I the said JAMES WATT have hereunto set my hand and seal this twenty‑ fourth day of August, in the year of our Lord one thousand seven hundred and eighty‑four.

JAMES WATT.

Signed and sealed, being first duly stamped, in the presence of JOHN SOUTHERN. ZACCHEUS WALKER,

Acknowledged by the within named JAMES WATT this twenty‑fourth day of August in the year of our Lord one thousand seven hundred and eighty‑four, before me, WILLIAM BEDFORD,

Master Extraordinary in Chancery.

INROLLED in His Majesty's High Court of Chancery, the twenty‑fifth day of August, in the year of our Lord 1784, being first duly stamped according to the tenor of the Statutes made for that purpose.

4.P.Y.

JOHN MITFORD.

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