The Wilkins Lecture: The 'Plain Story' of James Watt

The Wilkins Lecture: The 'Plain Story' of James WattAuthor(s): R. V. JonesSource: Proceedings of the Royal Society of London. Series A, Mathematical and PhysicalSciences, Vol. 316, No. 1527 (May 12, 1970), pp. 449-471Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/77633 .

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Jones Proc. Roy. Soc. Lond. A, volume 316, plate 5

James Watt, F.R.S. (1736-1819) (from Williamson's Memorials of James Watt).

(Facing p. 449)



Proc. Roy. Soc. Lond. A. 316, 449-471 (1970)

Printed in Great Britain

THE WILKINS LECTURE

The 'plain story' of James Watt

BY R. V. JONES, F.R.S.

(Delivered 20 November 1969-Received 2 December 1969)

[Plates 5 and 6]

In 1648, John Wilkins, who had just become Warden of Wadham and who was later to be the first Secretary of the Society, published his Mathematical Magick: or, the Wonders that may be performed by Mathematical Geometry; and in his Address to the Reader (Wilkins I648) he explained:

'I have now ventured forth this discourse; wherein besides the great delight and pleasure (which every rational Reader must needs find in such notions as carry with them their own evidence and demonstration) there is also much real benefit to be learned; particularly for such Gentlemen as employ their estates in those chargeable adventures of Drayning, Mines, Cole-pits, etc. who may from hence learn the chief grounds and nature of Engines, and thereby more easily avoid the delusions of any cheating Impostor: And also for such common Artificers, as are well skilled in the practice of these Arts, who may be much advantaged by the right understanding of their grounds and Theory.'

The Wilkins Lecture might therefore at any time be fittingly devoted to James Watt who, seeming to start as a common artificer, brought about the revolution in engine design that Wilkins foreshadowed; and all the more so in this bicentenary year of Watt's crucial patent for the invention of the condenser. In thanking Council for the honour of their invitation to give the Lecture on this special occasion, I have an added pleasure because it was Wadham, the College of John Wilkins, that gave me my undergraduate education.

At the same time, pleasure comes hand-in-hand with apprehension: for we may remark that the condenser was no less vital to our history than was Waterloo, that the year of Watt's patent was also the year of Wellington's birth and of Napoleon's and that it is no easier to say something significantly fresh about Watt 200 years after he invented the condenser as it will be about Wellington 200 years after Waterloo. Doubtless, there are contributions to scholarship that have still to be made about Watt, for his voluminous papers still survive, and it seems that eveu now there are some that are unexamined. From these papers Professor Eric Robinson, who recently contributed to Notes and Records, has just produced his study 'James Watt and the steam revolution' in which he provides a wealth of information well beyond anything that we can cover in this single lecture (Robinson

28 [ 449 1 Vol. 3I6. A. (I2 May i970)



450 R. V. Jones

I969). All that we can do here is to look at the merest outlines of Watt's life, and to concentrate on the factors that led him to the invention of the condenser and on its place in the Industrial Revolution and in Natural Science.

ANCESTRY

Among the factors in any advance made by an individual must surely be ancestry, environment and challenge. We know the ancestry of James Watt back to his paternal great grandfather, a farmer of Kildrummy, about 35 miles west of Aber- deen; and we may remark in passing that the country around Aberdeen was at that time producing men of science, headed by the Gregorys, out of all proportion to its population (Clement & Robertson I96I). There are still Watts in the parish of Kildrummy, and as far as local tradition can be believed, James's great grandfather had the Christian name of Thomas; pressed into the ranks of the Covenanters for the nearby battle of Alford in 1645, he was killed in their defeat by Montrose. His son, also Thomas had been born in 1642; and the orphan, after an upbringing by distant relatives, entered for Arts at Marischal College in 1668 (Anderson i898). He was therefore what we should now call a 'mature student'; and, although it does not appear that he graduated, he became a teacher. His subject, which he doubtless studied at Aberdeen as part of mathematics, was navigation; and it was to another seaport, Greenock, that he moved to earn his living. There he died in 1734; his tombstone describes him as 'Professor of the Mathematicks' (Muirhead I858, p. 4). He trained both his surviving sons, John (1687-1737) and James (1699-1782), in his own profession; John made a survey of the Clyde that was completed by James and James's two sons who were also named James (1736-1819) and John (1739-62). It is the work of the former that we are commemorating today.

The elder James Watt did not primarily pursue his father's training; instead he served as apprentice to a builder and shipwright, and he became a ship's chandler who among other things supplied and repaired navigational instruments. Thus his workshop was the place where his son James became familiar with tools and with optical instruments, and through them with astronomy. At home the tone was set by portraits of Napier and Newton hanging on the walls. Our James was a sickly boy, and he was partly taught at home by his father and mother, who before her marriage was Agnes Muirhead. When, at the age of 17, James had to choose a calling, he decided to qualify as an instrument maker; and so he went in 1754 to Glasgow and was there introduced by his mother's relative George Muirhead-the Professor of Latin-to various others of the university staff including Robert Dick, the Professor of Natural Philosophy. Dick sent Watt to London with a recommen- dation to Short (1710-68, F.R.S. 1737) the celebrated maker of telescopes, who arranged for Watt to work with John Morgan, an instrument maker in Cornhill. Watt spent a successful year or so with Morgan, but then, finding his health failing, he returned to Glasgow in 1756.



The Wilkins Lecture 451

THE GLASGOW ENVIRONMENT

After some months of uncertainty about setting up a shop, Watt was allowed to occupy premises in the university precinct, and to use the designation 'Mathe- matical-Instrument-Maker to the University'. Dick, the Professor of Natural Philosophy who had helped Watt to this status, unfortunately died within a few months; and without Dick's support Watt's business for the first year was not a financial success. But it is indicative of the progressive outlook of the University of Glasgow at this time that it was prepared to encourage an instrument maker, and Watt was now intimately placed in an extraordinarily favourable environment; for if Edinburgh at this time was having its golden age of culture with men like Hume, and the Adams Brothers, Glasgow was easily Britain's foremost University in Science and Technology. And three outstanding men associated with the Univer- sity, John Anderson, Joseph Black, and John Robison, were to figure particlarly in Watt's career.

John Robison (1739-1805), the youngest of the three, graduated in Arts in Glasgow in 1756. His enthusiasm for Natural Philosophy and Astronomy was such that Dick took him to see Watt's shop. 'After first feasting my eyes with the view of fine instruments, and prying into everything', later wrote Robison, 'I con- versed with Mr Watt. I saw a workman, and expected no more. But was surprised to find a philosopher, as young as myself, and always ready to instruct me. I had the vanity to think myself a pretty good proficient in my favourite study, and was rather mortified at finding Mr Watt so much my superior' (Muirhead I858 p. 61). Robison and Watt became life-long friends; and in a footnote in Robison's 'System of Mechanical Philosophy' Watt described his first acquaintance with the steam engine: 'My attention was first directed in the year 1759 to the subject of steam engines, by the late Dr Robison himself, then a student in the University of Glasgow, and nearly of my own age. He at that time threw out an idea of applying the power of the steam engine to the moving of carriage wheels, and to other purposes, but the scheme was not matured and was soon abandoned on his going abroad '(Robison I822, P. 113).

Robison left Glasgow to accompany Admiral Knowles as tutor to the latter's son on the naval expedition that culminated in the Battle of Quebec. Indeed, Robison was a midshipman in the very boat in which Wolfe recited Gray's Elegy below the Heights of Abraham, and it is to Robison that we owe the famous story, recording Wolfe's comment that 'He would prefer being the author of that poem to the glory of beating the French tomorrow' (Playfair I822, p. 126).

After Quebec, Robison was selected by the Navy to carry out the trials of Harrison's chronometer on a voyage to the West Indies, after which he returned to Glasgow in 1761. He was thus present during the period in which Watt invented and developed the condenser. In 1770 he left Glasgow for St Petersburg, where he in- structed the Navy of Catherine the Great in shipbuilding and navigation, and he returned to Scotland in 1774 as Professor of Natural Philosophy in Edinburgh,

28-2



452 R. V. Jones

where he later became the first Secretary of the Royal Society of that city. His lectures on the steam engine, published posthumously in 1822, contain important comments by James Watt.

The second member of the trio with whom Watt was associated particularly in Glasgow was Joseph Black (1728-99). He was Professor of Medicine and Lecturer in Chemistry, and he was in course of evolving the concepts of specific heat and latent heat. He first noticed that ice and snow do not disappear suddenly when the air temperature changes (Black I803, p. 117), and this led him to experiments that showed that a definite quantity of heat was required to change a given quantity of ice into water. These results were included in his university lectures from 1762 onwards, but it was some time before he extended the ideas to vaporization as well as to melting. Although he had contemplated the possibility, he had thought that heat sources would be too unsteady for reliable observations to be made. The critical step came when a distiller told him 'that, when his furnace was in good order, he could tell to a pint, the quantity of liquor that he would get in an hour' (Black I803, p. 157). Thus did technology contribute to science for, encouraged by this statement, Black in 1764 proceeded to quantitative experiments on the latent heat of vaporization; besides performing experiments for himself on 9 October, he encouraged Watt to make some more accurate experiments a few weeks later.

Watt was already interested in steam, because he had been asked by Anderson (1726-96), the Professor of Natural Philosophy, to overhaul the University's model of a Newcomen engine for demonstration to his students. Anderson, incidentally, was in the Wilkins tradition, for as early as I648 Wilkins had written in Mathematical Magick: 'Ramus hath observed, that the reason why Germany hath been so eminent for Mechanical inventions, is because there hath been publick Lectures of this kind instituted amongst them, and those not only in the learned languages, but also in the vulgar tongue, for the capacity of every unletter'd in- genious artificer.' This plea for technological education was echoed by Anderson, who tried to fill the gap in Glasgow by lectures that he threw open to unmatri- culated artisans. They became known as the 'anti-toga' lectures, and Anderson's defiance of academic convention incurred the enmity of his University colleagues. Their respect for him was not improved by his support for the French Revolu- tionaries, which went so far as to suggest that they should use the newly invented balloons to drop leaflets for propaganda purposes. And as an obituary act of defiance to his University colleagues, he left money to found a rival establishment in Glasgow, the Andersonian Institution, where Natural Philosophy and Technology should be-the main objectives. This Institution, started in 1798, is nowthe University of Strathelyde.

THE STEAM ENGINE BEFORE WATT

When, early in 1764, Anderson asked Watt to overhaul the Newcomen model, he thereby presented a challenge that by ancestry, training and environment Watt was uniquely fitted to ansmrer.



The Wilkin8 Lecture 453

Let us now see that challenge in the context of technological history. Here we may start with the depletion of the medieval forests of England during the six- teenth and seventeenth centuries, as industrial requirements for fuel rose in glass- making, soap-making and brewing, as well as in the manufacture of charcoal for the

SAVARYS

STEAM ENGINE.

L M1

I B

w8 r

i a

FiGuRE~ 1. Savery's engine, 1698 (from Robison's A system of mechanical philosophy, vol. ii, pl. i, fig. 6).

production of iron. As coke was gradually substituted for charcoal, it became essential to extract coal from mines; but mining would be limited by the seepage of water into the pits unless suitable pumps could be devised. With this in view Thomas Savery (? 1650-17 15) made a water pumping device which he patented and demonstrated to William III in 1698 and to the Society in 1699; it was based on a



454 R. V. J-ones

use of steam power suggested by the Marquis of Worcester (1601-67) in his Century of inventions, published in 1663. Steam from a boiler A (figure 1) is admitted to a receiver R, from which it drives the air; the steam then condenses and thereby creates a partial vacuum, which is used to suck water from the pit H. When the water has entered R the cocks C and D are so operated in conjunction with valves I and G that fresh steam from the boiler drives water out of R and up the 'chimney', whence it overflows to waste. R must, of course, be sited not more

a EWCOME NS S TEAM E NG INE.

m

z~~~~~~

d~~~~~~~~~~~~~

FIGURE 2. Newcomen's engine, 1705-11 (from iRobison, vol. II, pl. I, fig. 7).

than 30 ft or so above the water level in the pit, but the exhaust water can in principle be pumped to any desired height within the safety pressure limit of the boiler; but so low was this limit that, according to fRobison (I822, p. 54), the Savery engine was usually employed only to lift less than 40 ft.

Savery's engines were especially made and used in the tin mines of Cornwall, and among those mechanics who worked on them was Thomas Newcomen (1663-1729). Newcomen was acquainted with Robert Hooke (1635-1703) and raised with ilooke the possibility of exploiting a suggestion due to Papin (1647-1712 ?) the inventor of the 'pressure cooker', who had demonstrated in 1690 the idea of using steam to



The Wilkimn Lecture 455

drive a piston (Muirhead I858, p. 140). The construction of the first working engine with a piston was almost certainly due to Newcomen alone, but he allowed Savery to share the new patent (1705) with him, perhaps because the latter's original patent effectively blocked the whole field of steam power.

Figure 2 which, like figure 1, is taken from Robison's A system of mechanical philosophy, shows a diagram of Newcomen's engine. 'Let A' says Robison 'repre- sent a great boiler properly built in a furnace. At a small height above it is a cylinder CBBC of metal, bored very smoothly and truly'. At this point Watt, the practical engineer, prompted a footnote: 'This ought to have been the case, but Mr Watt found them generally very much otherwise (Robison i822, p. 59). The errors between piston and cylinder were taken up by a packing of leather or rope well filled with tallow, and the seal was made by a pool of water which rested on the top of the piston. When steam was admitted to the cylinder, the forces were such that the piston rose, pulled by the excess weight on the far side of the cross-beam from that to which the piston itself was attached by a chain. During this time air and wet steam were blown out through the snifting valve f. At the top of the stroke, water was injected into the cylinder from the cistern W and the steam condensed. When the vacuum was sufficient the atmospheric pressure acting on the top of the cylinder pushed the piston downwards, and this provided the working stroke which pulled downwards on the end of the cross-beam above the cylinder. The condensed water ran down the eduction pipe e into a cistern Y, and forced itself out through the valve h. Steam was then admitted again, and a continously cycling engine became possible. Newcomen's engine, which reached its working form between 1712 and 1717 had an immediate success and a long life. It continued to be made for many years, and to work for much longer. One specimen, erected in 1810 at Farme Colliery, Rutherglen, continued in service until 1915; it is now in the Science Museum. Newcomen's engines were large. The first had a cylinder of 21 in diameter and a working stroke of more than 6 ft. The effective vacuum was about half an atmosphere, giving a working force of about 14 tons. Operating at 14 strokes a minute, the engine would develop about 6 hp, while later engines had cylinders of up to 7 ft diameter and 10 ft stroke, developing more than 100 hp.

Newcomen's engines were used almost entirely for the raising of water. Indirectly, a few may have been used to drive machinery by pumping up water for a mill-dam and thus turning a water-wheel. Keane Fitzgerald in 1758 published in the Philo- sophical Transactions a proposal to generate rotation from the reciprocating motion of a Newcomen engine by adding teeth to a sector at the end of the main beam, and using these teeth to drive ratchet-wheels which would in turn give a unidirectional drive to a fly-wheel; but this does not seem to have progressed beyond a model. At least this is what Watt says in a footnote on p. 106 of volume ii of Robisons's Mechanical Philosophy; but in a letter (Muirhead I858, p. 280) of 1808 to his son he states that he had seen what seems to be the same system working at Hartley Colliery about 1768. Perhaps the lack of rotary applications for the Newcomen engine was due to its low efficiency; this did not matter so much in coal mining,



456 R. V. Jones

where fuel was plentiful, but it was a serious drawback if the steam engine were to be sited elsewhere. This problem attracted several men, including the great engineer John Smeaton (1724-92), who, like Watt, had started as an instrument maker and who established empirically in 1772 that the maximum thermal efficiency was reached with a vacuum of half an atmosphere. It was Smeaton who built the largest Newcomen engines mentioned in the last paragraph.

SCALES AND MODELS

The Newcomen engine, however, had been rendered potentially obsolescent even before Smeaton started his investigations. For Watt had seen, after Anderson had handed him the model engine, a much more penetrating approach to the problem of thermal efficiency. The model (figure 3, plate 6) still exists in the Hunterian Museum at Glasgow, and there are at least three first-hand accounts-Watt's (Robison I82z, p. 113-121) Black's and Robison's (see Muirhead i858, pp. 58-60 and pp. 60-73 respectively) -of what happened. Watt's is clearly the mostinte rest- ing; it is given as a note in Robison's Mechanical Philosophy, and it is supplemented by other accounts that he gave elsewhere (Muirhead i858, pp. 83-91). The model had previously been sent to Sisson the celebrated instrument-maker in London, but it still failed to work, and Watt describes how he set about repairing it 'as a mere mechanician'. Watt says that to his surprise he found that the 9-inch diameter boiler could not supply the cylinder (2-inch diameter and 6-inch stroke) with enough steam to keep it going for more than a few strokes. Then came a great flash of physical insight: 'It soon occurred that this was caused by the little cylinder exposing a greater surface to condense the steam than the cylinders of larger engines did in proportion to their respective contents' (Robison I82z, p. 114). He thus concluded that he was contending with an unfavourable scaling factor: the wall of the cylinder, which had to be alternately heated and cooled, wasted heat in direct proportion to its radius, whereas the volume of steam that it contained was proportional to the square of the radius.

One might fairly dispute the detail of Watt's reasoning at this point. The matter is one of heat supply and heat loss, the one being proportional to the surface area of the boiler, the other to the surface area of the cylinder, and so if boiler and cylinder are scaled down in the same ratio, the balance should be unchanged. What was not scaled down in the model was the thickness of the cylinder wall, as Mr R. J. Law has pointed out (I969). Since the wall was relatively much thicker in the model than in an actual engine, it took relatively longer to heat up and cool down, and so it was losing heat to the surroundings for a relatively longer time. The wall need only have been thick enough to resist atmospheric pressure, and thus could have been reduced in proportion to the radius, in which case it, too, would have scaled down in the same proportion as the surface areas. Probably, too, leakage of air past the piston was relatively more important on the smaller scale of the model.

Further evidence regarding the cause of failure of the model may well be derived



Jones Proc. Roy. Soc. Lond. A, volume 316, plate 6

FIGURE 3. The Newcomen model belonging to the University of Glasgow, which Anderson asked Watt to overhaul in 1764 (from Memorials of James Watt by George Williamson, published by Constable, 1856).

(Facing p. 456)




from work currently in progress at the University of Manchester Institute of Science and Technology, where Mr Flowett of the Department of Mechanical Engineering has made a model of much the same size as that which Watt was asked to repair. It works satisfactorily at about 15 strokes per minute and Dr A. P. Hatton says that experience with the model makes it seem that air leakage would have been a more important source of trouble than the thickness of the cylinder wall.

If the cause of the trouble seemed to come quickly to Watt, its solution took him much longer. He started work on the model, he says, during the winter of 1763-4, and by shortening the column of water in the pump and by moderating the injection, he could make the model work regularly. He seems to have left the model in this condition, and then turned to make further models of his own.

In the first of his new models he tried to reduce the heat lost in the cylinder by using wood instead of brass for its walls, and by increasing the proportions of the cylinder to 6 in diameter and 12 in stroke; but this engine, too, was inefficient, and he began experiments to ascertain the extent of the heat lost to the cylinder walls. He was surprised by the quantity of water that had to be injected to condense a given quantity of steam, and he thereupon consulted Black, who explained his doctrine of latent heat. Armed now with the experimental fact, which he had dis- covered independently of Black, and with Black's new doctrine, he was able to de- fine the problem. He expressed it in a further account (Muirhead I858, pp. 83-91) that he gave in 1796 to the Court adjudicating on the validity of his patent, and which he entitled 'A Plain Story'. There he states 'that he turned the matter over in every shape, and laid it down as an axiom that to make a perfect steam-engine, it was necessary that the cylinder was always as hot as the steam that entered it, and that the steam should be cooled down below 1000 (Fahrenheit) to exert its full powers'. The first condition was to avoid the dissipation of heat by the alternate heating and cooling of the cylinder walls, the second to reduce the vapour pressure of the condensed water to a stage where it could be neglected in comparison with the atmospheric pressure on the outside of the piston.

THE SEPARATE CONDENSER

The two conditions seemed mutually exclusive, and it was months before Watt saw the answer. It came to him, he told John Hart, (Muirhead I858, p. 82), one Sunday afternoon on a walk 'In the Green of Glasgow, and when about half-way between the Herd's house and Arn's Well, my thoughts having been naturally turned to the experiments I had been engaged in for saving heat in the cylinder, at that part of the road the idea occurred to me, that, as steam was an elastic vapour which would expand, and rush into a previously exhausted space; and that, if I were to produce a vacuum in a separate vessel and open a communication between the steam in the cylinder and the exhausted vessel, such would be the consequence'.

Watt rapidly considered the details involved in the improvement. He chose to remove the water and air from the condenser by a pump, and to replace the



458 R. V. Jones

water-seal of the Newcomen piston by a better fit independent of wax or tallow; and he proposed, by adding a stuffing-box at the top of the cylinder, to reduce the cooling effect of the atmosphere on the inner wall as it became exposed by the descent of

(a)

FiGuREE 4. Condenser (a, side view and b, from above) and piston (c), from Watt's first condensing model, 1765 (by courtesy of the Director of the Science Museum, London).

the piston. He used an anatomist's brass syringe for his first condenser, which he states. in Robison to have been 11 in in diameter and in 'A Plain Story' as 2 in. Mir R. J. Law of the Science Museum has investigated the evidence and has found

what is very probably the piston of this first engine. It was among the contents of




Watt's workshop, which has for many years been on display in the Museum. The first condenser, which was of tin plate, has also survived (figure 4). At least one other model and perhaps a further one. Mr Law summarizes his investigations in a Science Museum monograph published this year (I969) on 'James Watt and the Separate Condenser' and those who are interested should at this point refer to Mr Law's account.

inhe9 1 2 3 4

FIGuRE 5. Section through Watt's first condensing model, conjecturally completed, by Mr R. J. Law (by courtesy of the Director of the Science Museum, London).

The surprising survival of these fragments is probably due to the fact that Watt had the true academic abhorrence of destroying anything that might later be of any interest either to himself or posterity. His workshop still contains, for example, guitar components that he must have made when his shop was not fully busy on scientific instruments. He had in the meantime moved his shop from the University precincts to the Salt Market and thence, by 1 December 1763, to the Trongate (Muirhead I858, pp. 44-46; Rolt i962); he evidently built up a considerable business, for at one stage he was employing sixteen journeymen.

For more than a year after the idea of the condenser came to him Watt experi- mented with different designs, evolving both the multi-tube and multi-plate



460 R. V. Jones

versions. Black lent him ?1000, and introduced him to Dr John Roebuck (1718-94), an English inventor, who had made a fortune by replacing the glass vessels by leaden ones in the manufacture of sulphuric acid, and who had in 1759 established the Carron Ironworks in Stirlingshire. Roebuck intended to substitute coke for charcoal in iron smelting, and was therefore thinking of mining his own supply of coal. He had acquainted himself with the Newcomen engine, and being thus sensitive to any prospect of an improvement in its performance, he became very interested in Watt's experiments.

F ULL-SCALE FAIL URE

The first models were sufficiently encouraging for Watt and Roebuck to agree to build a full-scale piston engine at Kinneil, Roebuck's estate on the Linlithgow coalfield in 1766. But progress was slow because Watt could not get a true enough cylinder; and he spent much time on an altogether different and pistonless design, or 'steam wheel', which was as distinct in concept as the Wankel is from the ordinary internal combustion engine. Roebuck's fortune was dwindling, and Watt himself was in financial difficulty because of the death of John Craig, his partner in the shop. Watt therefore almost forsook the engine in order to keep himself solvent by acting as surveyor for the Forth-Clyde Canal. In connexion with this project, he had to appear before Parliament in London; and on the way back he met William Small (1734-75) in Birmingham and Erasmus Darwin (1731-1802, F.R.S. 1761) in Lichfield. Small took him to see the great 'manufactory' of Matthew Boulton (1728-1809, F.R.S. 1789) at Soho on Handsworth Heath.

The next year, 1768, Watt was in Birmingham again, for in the meantime Roe- buck had been sufficiently impressed by the prospects of the engine to advance Watt ?1000 with which to repay Black, and a further ?120 or so for the securing of a patent, in return for a two-thirds interest in any proceeds that might arise. The patent for the condensing engine, whose bicentenary we are now celebrating, was therefore drawn up; and Roebuck sent Watt to London to secure protection. This time, on the way back, Watt met Boulton himself.

Boulton was already employing 600 craftsmen in the manufacture of typically Birmingham ware such as buckles, buttons, and watch-chains, mainly in steel; he also specialized in ormoulu. He was both an inventor and an organizer and he im- mediately appreciated the talents of his visitor; he proposed that he should join Watt and Roebuck in the steam enterprise. But Roebuck would offer him a licence to manufacture the engine in three counties only, and Boulton's vision and enthusiasm are evident from his reply (9 February 1769): 'I would erect all the conveniences necessary for the completion of engines, and from which manufactory we would serve all the world with engines of all sizes.... It would not be worth my while to make for three counties only, but I find it very well worth my while to make for all the world' (Rolt I962, pp. 47-48; Dickinson 1925, p. 54). But Roebuck would not budge, and yet he could not help Watt as he himself drifted towards bank- ruptcy, a victim of his own plans and of a national wave of financial depression.




Watt continued to keep himself by surveying, and in 1773 planned the course of the Caledonian Canal. The breadth of his interests is indicated by a letter that he wrote to Mr George Clerk-Maxwell, one of the Commissioners of H.M. Customs in Scot- land, and great-grandfather of James Clerk-Maxwell; the letter described Watt's investigation of a vitrified fort on a hill just north of Inverness (Williams I777).

Watt was at this time near despair for the future of the engine, and wrote to Boulton on the winding up of Roebuck's affairs 'None of his creditors value the engine at a farthing'. Boulton was then able to secure Roebuck's two-thirds interest in the patent, and the famous partnership of Boulton and Watt started.

BOUTLTON AND WATT

It was a marvellous partnership. The two men complemented one another ideally. Watt, the inventor and scientist, knew enough about organization to appreciate its problems-had he not himself had sixteen journeymen in Glasgow? He knew that one reason for the previous failure of his engine was, as he wrote to William Small in 1772 'The work done is slovenly, and our workmen are bad, and I am not sufficiently strict' (:Roll I930, p. 13), and he 'would rather face a loaded cannon than settle an account or make a bargain' (Roll I930, p. 20). Boulton the organizer and entrepreneur, was enough of an inventor to appreciate Watt's technical problems. His forthright and optimistic joviality contrasted with Watt's quick temper and and morose outlook. As he wrote to Watt 16 April 1781: 'I cannot help recom- mending it to you to pray morning and evening, after the manner of your countrymen (The Scotch Prayer " The Lord grant us a gude conceit of ourselves ") for you want nothing but a good opinion and confidence in yourself and good health.'

When Watt removed the so far unsuccessful Kinneil engine to Birmingham in 1774, the partnership was at first informal. Boulton wanted to confirm his belief in the engine by seeing Watt get it to work, and to be assured about the future of the patent, which had already run for five of its thirteen years. The main trouble at Kinneil had been the misfit of the piston and cylinder, and Boulton asked his friend John Wilkinson (1728-1808), the Staffordshire ironmaster who pioneered the substitution of coke for charcoal in iron smelting, to make a new cylinder.

Wilkinson, who was the brother-in-law of Joseph Priestley, incidentally cast his own coffin in iron (it proved to be too small to contain him when he died) and astonished many sceptics by floating an iron boat on the Severn. When Boulton approached him, he had recently perfected a boring mill for cannon; and he brought his technique to bear on the boring of Watt's 18-inch cylinder to such effect that Watt soon had the engine running successfully; and, thanks to Boulton's skilful handling of its Members, Parliament agreed to extend the 1769 patent for twenty- five years.

The partnership was now firmly started. Spurred by Boulton, Watt had a 50- inch cylinder engine working at Bromfield Colliery, Tipton, by 8 March 1766, and shortly afterwards a blowing engine for Wilkin's ironworks. One of the earliest



462 R. V. Jones

engines, in a distillery at Stratford-le-Bow, was running well when it was inspected by Smeaton in April 1777, but his visit led to disaster, for 'He gave the engineer money to drink and the consequence of that was that ye next day the engine was almost broke to pieces' (Dickinson 1925, p. 95). For the first 20 years Boulton and Watt did not manufacture complete engines: they undertook to furnish designs, to supervise the erection of the engines, and to manufacture only those difficult parts for which their factory alone had the special skills. Almost invariably they recom- mended that the cylinder should be made by Wilkinson. After his first experience of Wilkinson's work, Watt wrote enthusiastically to Smeaton 'Mr Wilkinson has improved the art of boring cylinders so much that I promise upon a 72-inch cylinder not being from absolute truth more than the thickness of a thin sixpence in the worst part'. Wilkinson's achievement was indeed outstanding: it represented an error of about one part in a thousand, and even by 1900 boring mills were rarely more than twice as good as this (Kranzberg & Pursell I967). Wilkinson's vital improvement to the boring mill had been through realizing that the cylinder was open at both ends, and therefore that he could support the bar carrying the boring tool at both ends, instead of one end only, as had been the practice in earlier machines

(Rolt I965). Boulton and Watt asked their customers to pay on the basis (Roll 1930, p. 31) of

one-third of the cost of the coal saved by their engine in comparison with an ordinary engine of Newcomen design (but not one of Smeaton's !). Part of the basis of reckoning was the number of strokes made by the engine, and so Watt invented a suitable counter. The subsequent history of the partnership forms one of the most interesting chapters in the whole of industrial history; and although we must reluc- tantly keep to more technical matters, we ought to remember what an outstanding industrialist Boulton was. Hfis professional skill and exhuberant patriotism are well shown by one of his last acts, which was to strike a medal of Nelson after Trafalgar, with the 'England expects... 'signal on the reverse, and to present one to every man in the British Fleet that had fought the battle.

TEIE PARALLEL MOTION

The installation of the early engines involved Watt in much work outside Birmingham, but he was continually trying new improvements. His first engines had followed Newcomen's in depending on atmospheric pressure for the working stroke, with steam pressure merely lifting the piston back for its next working stroke. By 1782, he was using steam itself for the working stroke, and allowing the latter part of this stroke to be effected by the expansion of the steam already in the cylinder, and thus resulting in economy. He also made the engine to have a double action-by injecting steam alternately above and below the piston while evacuating the spent steam on the other side of the condenser. For this he needed to guide the piston rod more positively than by the simple chain of his original design. He hit on a solution of this problem which so pleased him that, surveying his life's achievements in 1808 he wrote to his son 'Though I am not




over-anxious after fame, yet I am more proud of the parallel motion than of any other mechanical invention I have ever made' (Muirhead i858, p. 294).

Let us see how Watt developed the motion; figure 6 shows his own sketch. First he saw that if two equal rods AB, CD, pivoting about B and C respectively, are joined by a link AD, the mid-point E of AD will describe an approximately straight line as A and D move along their respective arcs. The best configuration (Willis I870) depends on the desired length of stroke, and for this the link AD should be off-set from the vertical, when AB and CD are parallel and horizontal, by

4

c:

C D~~

At0

c< E -

F

C FIGURE 6. Watt's parallel motion, 1783. At top, Watt's own sketch; right, optimum setting

for drop-link AD; bottom, full motion with pantograph.

an angle equal to the inclination of the link on the other side of the vertical when AB and CD are at the two limiting configurations of the stroke. If the problem were merely to provide a straight line motion, it was thus already solved; but Watt added a pantagraph AFGD which besides aiding a compact and convenient design provided a second straight line motion parallel to the first. In the simplest case the geometry is such that OD = FA - AB, and FG = AD. Then FG must be

parallel to AE, and so BAE = BFG. In the triangles BAE and BFC, we also have PB = 2AB, and FP = 2AE. Therefore these triangles are similar, and so GEB is a



464 R. V. Jones

straight line, pivoting about B, and BG = 2BE. Any motion of E is therefore repli- cated by G on twice the scale; and since E describes a straight line, G will move along a parallel straight line at twice the speed of E. Watt connected the top of his piston rod to G, and at the same time used the straight line motion of E to operate his valve gear.

It is surprising how precisely straight lines can be generated in this way. Eight feet of stroke with a deviation not greater than a fortieth of an inch was typical of Watt's engine, with such compact dimensions as BF = 12 ft, AD = 4 ft. There is a fascination, first experienced by Watt himself, in watchinig the mechanism execute its function: it is truly one of 'the wonders that may be performed by mechanical geometry'. It led to much theorizing about linkages that culminated in Peaucellier inventing the true straight line motion in 1864, although Tchebecheff was still trying to prove some years afterwards that such a motion would be impossible. Peaucellier's linkage was incidentally demonstrated to the Dining Club of the Royal Society less than 200 yards away from the site of this lecture, in the hall of the Athenaeum; Sylvester (I909) records that Lord Kelvin was so fascinated that he refused to hand the model on to his neighbour, exclaiming that 'It is the most beautiful thing that I have ever seen in my life'.

THE ALBION MILL

The parallel-motion linkage and others of Watt's devices can be seen in the drawing (figure 7) of one of the engines for the Albion steam flour mill, which was erec- tedin 1788 byJohn Rennie (1761-1821, F.R.S. 1798, andwhosubsequentlydesigned the old Waterloo Bridge) on behalf of Boulton and Watt. The success of this engine, even though it was burned down in 1791, led to the general introduction of steam power for flourmilling and for other rotary machinery; this application had been quickly seen by Boulton, who had wisely steered Watt's energy in this direction perhaps against Watt's inclination, and certainly against that of Smeaton, who maintained that rotary motionl was best derived by pumping water over a wheel.

The centrifugal governor that can be seen in figure 7 was supplied by Watt to regulate automatically the speed of the engine by moving the throttle; it was probably the first application of self-regulating control to an engine. Watt derived the idea from a letter by Boulton, who had seen a centrifugal governor applied in the Albion Mill to the milling rollers, so that the faster they went the harder they ground. The development of the governor following its invention by Watt led to the laying of the theoretical foundations of automatic control by Maxwell in his classic paper of 1868 in the Proceedings (Maxwell i868).

The Albion Mill drawing also shows one of Watt's more cumbersome devices, said to have been originally due to William Murdock, the sun and planet motion for developing rotation from an oscillating cross-beam. He ultimately replaced the sun and planet wheels by a simple crank, which he would probably have used from the




beginning had not this device been patented by a rival. In fact, the crank had been invented long before in ancient China, and had been used by Leonardo da Vinci (Needham I969). Watt had a strong independence which sometimes drove him away from simplicity, if this simplicity was already being exploited by someone

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FiGU:.E 7. The Albion Mill Engine, 1788 (from Robison, vol. II, pi. V).

29 Vol. 3I6. A.



466 R. V. Jones

else; he probably spent more time, for example, on variations of packing methods for the piston and on variants of the condenser than was strictly necessary, perhaps because he was too proud to follow slavishly the methods already used by Newcomen.

THERMODYNAMICS

At the same time, some of Watt's innovations were extremely effective. Amongst these was the steam pressure indicator, which he made to drive a pencil trans- versely across a chart which moved longitudinally with the piston, thus automatically drawing a diagram in which steam pressure was plotted against the volume of the steam in the cylinder. From this diagram, the work done per stroke could be assessed, and Watt related this to his estimate of what a horse could do in a horse-mill. After trials with one of the horses belonging to Barclay and Perkins, he finalized a unit of horse-power as 33 000 ft lb/min (Crowther i962).

The indicator diagram has ever since been familiar to generations of engineers and, in the particular form of the Carnot cycle, to schoolboy physicists. Indeed, Carnot was inspired by the development of the steam engine in Britain to write in 1824 his RMflexions sur la puissance motrice du feu (Carnot 1824), in which he observed that steam was the source of Britain's power, and was more important to her even than the Navy of which she was so proud. He went on: 'Si l'honneur d'une decouverte appartient a la nation otu elle a acquis tout son accroissement, tous ses developpements, cet honneur ne peut etre ici refuse a l'Angleterre: Savery, New- comen, Smeathon, le celebre Watt, Woolf, Trevetick et quelques autres ingeni- eurs anglais sont les veritables createurs de la machine 'a feu; elle a acquis entre leurs mains tous ses degres successifs de perfectionnement. I1 est naturel, au reste, qu-une invention prenne naissance et surtout se developpe, se perfectionne, la oiu le besoin s'en fait le plus imperieusement sentir.'

Carnot made the vital observation that steam engines always needed a source of cold as well as a source of heat. We may well speculate, as Professor R. S. Silver has done, whether Carnot would have developed this concept so early had Watt not so clearly isolated the cooling function into the separate condenser. If the non-condensing engine had happened to come first, Carnot would have needed even greater insight than that which he showed when, starting with the condensing engine, he remarked that venting the steam directly into the atmosphere was the equivalent of condensing it at a temperature such that the vapour pressure of water was equal to atmospheric, which is, of course 100 'C.

HIGH PRESSURES AND LOCOMOTION

The non-condensing engine was actually covered in the fourth of Watt's claims in the patent of 1769, and the idea went back to Leupold in 1725 (see Ewing I902,

p. 22). Watt did not pursue this development since it needed high-pressure steam, and he thought that high pressure boilers would be dangerous; his own engines




usually worked at 7 pounds or less per square inch above atmospheric pressure. It could be argued that his preoccupation with safety retarded the introduction of high-pressure engines, but there is no cause to suspect his motive on the grounds of personal interests; in our own time, we in Britain were slow to develop the super- sonic aeroplane because of an understandable preoccupation with the safety of pilots. In the event, it was left to Trevethick in England and Evans in America to develop the non-condensing high-pressure engine early in the nineteenth century.

FIGU:RE 8. Murdock's model locomotive, 1784 (from Muirhead's Life of James Watt, p. 450)

The special advantage of this engine is simplicity and the saving of weight, which are of particular value in automotive applications. In fact, this was the goal which Trevethick succeeded in reaching in 1804, when he made a full-scale railway locomotive. The first model locomotive carriage had been made 20 years before by. Watt's brilliant assistant, William Murdock (1754-1839, Rumford Medal 1808). Murdock was at that time concerned with the erection of stationary engines in Cornwall, and built his little locomotive while living in Redruth. He had no railway on which to try it, but relied on the steep sides of a lane leading to the local church to guide it on its way. The trial had to be made at night, because he was working at a mine during the day, and the engine ran so well that it soon outdistanced him. It is recorded (Muirhead I859, p. 439) that 'shortly after he heard distant shouting, like that of despair; it was too dark to discern objects, but he soon found that the cries for assistance proceeded from the worthy pastor, who, going into the town on business, was met in this lonely road by the fiery monster, whom he subsequently declared he took to be the Evil One in propria persona'.

29-2



468 .R. V. Jones

EFFICIENCY

It is evident from the thermodynamic theory formulated by Carnot that the efficiency advantage of condensing over non-condensing engines decreases at high pressures, since these pressures necessarily require higher source temperatures and it therefore matters less whether the sink temperature is 100 ?C or 0 'C. Even so, the advantage is still considerable. Ewing, giving figures around 1900 (Ewing 1902,

pp. 175-184), quoted a steam consumption of 19.2 lb/h per horsepower (and a thermodynamic efficiency around 10 %) for the best non-condensing engine while the best condensing engine achieved 12.2 lb (and a thermodynamic efficiency of 19 %), both types of engine having boiler pressures of 160 to 170 lb/in2. It is not easy to make a direct comparison of Watt's and Smeaton's engines with these figures; Smeaton's engines are said to have done seven to ten million foot-pounds of work per bushel of coal (95 lb), while Watt's engines achieved twenty to thirty million foot-pounds when maintained with Watt's supervision (Rolt I962, p. 82). To make a comparison with the engines of 1900, one would have to assume a figure for the boiler efficiencies and this-I understand from Professor J. Diamond is unlikely to have been more than 25 %. If so, Smeaton's engines might have had a thermodynamic efficiency of about 3 %, and Watt's about 10 %. On this evidence, therefore, Watt roughly trebled the performance of steam engines in his time, and went more than half way to the performance achieved at the end of the nineteenth century.

The original Boulton and Watt partnership lasted until the 1769 patent expired in 1800; after that time they gradually handed over to their sons, who continued to expand the business. Nearly 500 engines had been built under the partnership, of which more than 300 were of the rotary type (Hinton I969-70). The durability of the machinery became one of the legends that gave the phrase 'made in England' so much meaning throughout the nineteenth century world. Perhaps somewhere there are Boulton and Watt engines still working; certainly a single-acting beam engine with injection condenser and built in 1809 was in regular work as recently as 1952, and it may soon be working again. It is at Crofton in Wiltshire, and it was used to pump water from Wilton Water into the Kennet-Avon Canal. It only stopped working when the Canal was abandoned, and a group of enthusiasts is trying to get the engine going again; the parallel motion linkwork, the piston, and other components, are free, and it is hoped to raise steam in a few month's time.

EPILOGUE

In an age when attempts are being made to pull great men down to the common level, especially if they are British, when it is being argued that Nelson went into Trafalgar deliberately to die, it is inevitable that it should be asked whether James Watt was as great a man as generations of his countrymen believed him to be. Was it just luck that he happened to work in Glasgow at the time when Joseph Black



The Wilkins Lecture 469-

was formulating his ideas about latent heat, or that young John Robison was thinking about steam, or that John Anderson was conscientiously trying to show his elementary students how a Newcomen engine worked ?-and all this at a time when the Clarendon Code applied to England but not to Scotland (Darlington I969). And was it just luck that brought Watt's invention to the notice of Matthew Boulton just when Britain was embarking on the Industrial Revolution, and when Boulton was perhaps the one man who could push the invention through to industrial per- fection, and when John Wilkinson had just found how to make a true cylinder? Was it luck that brought James Watt such brilliant engine erectors as John Rennie and such talented and faithful assistants as William Murdock? The answer to each of these questions must to some extent be 'yes!' But luck by itself cannot supply the complete answer. One aspect of greatness is the taking of the tides of fortune at the flood, and this Watt-despite his diffidence somehow did. He was indeed one one of a band so effectively described by H. A. L. Fisher (I936):

'A small handful of remarkable Scots and Englishmen, fewer than would be required for a football match, succeeded by their ingenuity in transforming the economic life of the country. No doubt they derived support and inspiration from the atmosphere of their age. Science had been spreading its influence ever since Francis Bacon preached the value of the Inductive Method, and some of the in- ventors, notably James Watt, who first gave a decisive industrial value to the steam engine, were men of science. Yet more important than actual scientific training was the idea, which the Royal Society had so powerfully helped to spread, that knowledge was a growing thing, and that by observation and experiment new truths could be brought to light.'

Fisher's description of James Watt as a man of science as well as an inventor is easy to justify. 'Observare' was, indeed, his own chosen motto; and if the evident thoroughness of his steam investigations is not enough, then we can turn to his anticipation of Cavendish's conclusion that water is a compound of hydrogen and oxygen. It was a happy outcome of the controversy over priority in this matter that led Cavendish to sign Watt's proposal form for Fellowship and (both Watt and Boulton were elected in 1785) for them to enjoy together 'a turtle feast' at the Society's Dining Club in 1785 (Muirhead I858, pp. 385-388). We can point, too, to Watt's mastery of other branches of science, where fronm his knowledge of optics he he was able to invent one form of the optical micrometer (Muirhead I858, pp. 321- 322). And he was a leading member of that remarkable association of men of science and of technology, the Lunar Society of Birmingham. Finally, he had what is often a characteristic of an analytical man of science, an elegant economy of expression. Has anyone since described Watt's contribution more tersely than he did himself in Robison's System of mechanical philosophy?

'In most of our great manufactories, these engines now supply the place of water, wind, and horse-mills, and instead of carrying the work to the power, the prime agent is placed wherever it is most convenient to the manufacturer' (Robison i 822,

p. 135).



470 R. V. Jones

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FIGURE 9. Proposal form of James Watt for Fellowship 1785.




As Watt told it, his life may have been a plain story; but through it we can see in superb colour the vigour of the eighteenth century at its best. Watt's simple act of bringing the prime mover to the place where the manufacturer wanted it, at the very moment of history when he wanted it, made Britain the workshop of the world; it transformed human society. My Lord President, I beg leave to conclude by quoting the motion (Arago i839), proposed in 1824 by your predecessor in office, Sir Humphry Davy, at the meeting that led to the erection of Watt's Memorial in Westminster Abbey: 'That the late James Watt, by the profound science and original genius displayed in his admirable inventions, has, more than any other man of his age, exemplified the practical utility of knowledge, enlarged the power of man over the external world, and both multiplied and diffused the conveniences and enjoyments of human life.'

REFERENCES

Anderson, P. G. I898 Records of Marischal College, vol. ii, p. 135. Aberdeen; New Spalding Club.

Arago, D. F. J. I839 Historical Eloge of James Watt (translated by J. P. Muirhead), p. 194. London: Murray.

Black, Joseph, I803 Lectures on the elements of chemistry (ed. by Robison), vol. i, p. 117. London: Longman & Rees.

Carnot, S. I824 R6flexions sur la puissance motrice du feu. Paris: Bachelier. Clement, A. G. & Robertson, R. H. S. I96I Scotland's scientific heritage. Edinburgh: Oliver &

Boyd. Crowther, J. G. I962 Scientists of the Industrial Revolution, p. 165. London: Cresset Press. Darlington, C. D. I969 The evolution of man and society, p. 512. London: Allen and Unwin. Dickinson, H. W. 1925 James Watt. Cambridge University Press Ewing, J. A. 1902 The steam engine, p. 22. Cambridge University Press. Fisher, HI. A. L. 1936 A history of Europe, p. 779. London: Arnold. Lord iinton I969-70 James Watt. Proc. Inst. Mech. Engrs. 184, part 1. Kranzberg, M. & Pursell, C. W., Jun. (editors) I967 Technology in western civilization, vol. i,

p. 272. Oxford University Press. Law, R. J. I969 Jarmes Watt and the separate condenser. London: H.M.S.O. Maxwell, J. C. i868 Proc. Roy. Soc. Lond. A 16, 270. Muirhead, J. P. i858 The life of James Watt. London: Murray. Muirhead, J. P. I859 The life of James Watt, 2nd edn. London: Murray. Needham, J. I969 The grand titration, pp. 95-96. London: Allen and Unwin. Playfair, J. i822 Works, vol. iv, p. 126. Edinburgh: Constable. Robinson, E. I969 James Watt and the steam revolution. London: Evelyn, Adams & Mackay. Robison, J. I822 A system of mechanical philosophy, vol. ii, p. 113. London: Murray. Roll, E. 1930 An early experiment in industrial organization. London: Longmans. Rolt, L. T. C. I962 James Watt, p. 21. London: Batsford. Rolt, L. T. C. I965 Tools for the job, p. 54. London: Batsford. Sylvester, J. J. i9o0 Mathematical papers, vol. iII, p. 11. Cambridge University Press. Williams, J. I777 An account of some remarkable ancient ruins, p. 75. Edinburgh: Creech. Wilkins, J. I648 Mathematical magick, or the wonders that may be performed by mechanical

geometry. London: Richard Baldwin. Willis, R. I870 Principles of mechanism, p. 354. London: Longmans.



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The Wilkins Lecture: The 'Plain Story' of James Watt