CHAP. IV., 1.] 



MECHANICS. WATT. 



69 



andconncc-niistry and Natural Philosophy (Dr Black and Dr 

 Dick), who had obtained for him his appointment, 

 must have been also his chief academical employers ; 

 and we may safely conclude that Watt constructed 

 much of Dr Black's apparatus, as he was certainly 

 admitted to intimate and confidential intercourse with 

 that great and amiable man. Dr Black removed to 

 Edinburgh in 1766, but the friendship which he had 

 extended to the young mechanic remained unaltered 

 during their joint lives, although their personal in- 

 tercourse must have been extremely slight after that 

 time. Now Watt's first thought of improving the 

 steam-engine dates (as we shall see) from the session 

 1763-4, the last but one of Black's stay in Glasgow ; 

 their intimacy was therefore fully established by that 

 time ; and we find Watt acknowledging his " obliga- 

 tions to him for the information received from his 

 conversation, and particularly for the knowledge of 

 the doctrine of latent heat;" 1 and we also find that 

 during Watt's experiments on steam subsequent to 

 the last-mentioned date, Black was cognizant of them, 

 and assisted in their contrivance. 2 Moreover, Watt 

 admits Dr Cullen's well-known experiment of redu- 

 cing the temperature of ebullition under the air-pump 

 to have been one of his starting points in the im- 

 provement of the steam-engine. 3 Yet this experiment 

 was not published until 1770, 4 and Watt must have 

 heard of it from Black himself, or from some one 

 attending his lectures, where the fact was almost cer- 

 tainly mentioned. Whether formally a student of Dr 

 Black's chemistry class or not, it is therefore evident 

 that Watt enjoyed advantages in the prosecution of 

 experimental physics which nineteen-twentieths of 

 enrolled students never attain. He had the privilege 

 of unreserved personal intercourse, amounting at last 

 to intimate friendship, with the first authority of the 

 last century on the subject of Heat, and one of the 



most cautious and accomplished of inductive philo- 

 sophers. 5 Watt's eminent merits, and doubtless his 

 merits alone, gained him this happy position ; bxit 

 had he remained either at Greenock, or with the op- 

 tician in Cornhill, he might have failed to combine 

 so admirably as he did the character of the practical 

 man and the philosopher. His place in science was His posi- 

 well typified by his position in Glasgow. His was tion in 

 the workshop within the College." Whilst the la- 

 boratories of the classes of Chemistry and Natural 

 Philosophy must have been his familiar resort, his 

 own rooms were frequented by the most intelligent 

 students, including his contemporary Dr Robison, 

 where subjects of science particularly connected with 

 mechanics were diligently canvassed. The extent of 

 his knowledge and the variety of his resources were 

 fully tested, and the result, as stated by the generous 

 pen of Robison, was a conviction of the superiority of 

 Watt in these respects to any of his contemporaries. 



It is a fact worthy of note that the immediate oc- (319.) 

 casion of Watt's improvements was the commercial Watt's first 



consideration of economy. In 1763 or 1764, being expe . n ~ 



% . ments ou 



called on to repair a model 01 the Atmospheric En- steam. 



gine in the Natural Philosophy class at Glasgow 

 (which model is, still preserved), he found the amount 

 of steam expended in heating the cylinder at each 

 stroke to be so great that the boiler was insufficient 

 to supply it properly. He then commenced experi- 

 ments on the amount of steam thus consumed, and on 

 the means of diminishing it. Though the primary ob- 

 ject was the repair of a model, it is not to be doubted 

 that Mr Watt had in view the practical improvement 

 of the engine on the great scale, with the use of which 

 in the coal-fields of the west of Scotland he was pro- 

 bably familiar, having the intention of becoming 

 himself a civil engineer, and being already acquainted 

 with the writings of Desaguiliers and Belidor. 6 



mentality of his mother's kinsman Mr George Muirhead, who had then (1754) just exchanged the professorship of oriental lan- 

 guages for that of Latin." It will be seen that this refers to a period antecedent to his journey to London. 



1 Letter to Dr Brewster in Robison's Mechanical Philosophy, ii., p. v. 



9 Robison's Mechanical Philosophy, ii., 115, note (by Mr Watt). 



3 Ibid., p. vii., and 114, note. 



* In the Edinburgh Physical and Literary Essays, vol. ii., Dr Black (who was intimate with Cullen) knew of it at least in 

 1757. Lectures, i., 525. 



6 It is perhaps unfortunate that Mr Watt, when on the verge of fourscore, contrary to his ovn intentions, but yielding to u the 

 representation of friends," recorded a complaint that his best friends, Black and Robison, had refused him his due share of merit 

 in the improvement of the steam-engine, and disclaimed, as injurious, the appellation of "a pupil of Dr Black" (letter to Dr 

 Brewster in Robison's Mechanical Philosophy, vol. ii., p. v.) Admitting (as he does on the same page) that the doctrine of latent 

 heat was due to Dr Black, and that he first learnt it from him, he adds, " this theory did not lead to the improvements I after- 

 wards made in the engine," p. viii. No one ever ascribed to Black the beautiful invention of a separate condenser, but even 

 Watt's most ardent eulogists (Lord Brougham and M. Arago) admit that the theory of latent heat " forms the key to the econo- 

 mical appreciation of the steam-engine." So far was Watt from being independent of Dr Black's assistance in this matter, that 

 he himself tells us twice over, in substantially the same language, that when in the course of his experiments on the model engine 

 in Glasgow College in 1764 he was " at a lots to understand how much cold water could be heated by so small a quantity in the 

 form of steam," he "applied to Dr Slack, and then first understood what was called latent heat" (Robison, ii., p. v. ; also p. 116, 

 note). Mr Watt might have been the discoverer of latent heat, and the solver of his own dilemma, had not Dr Black been at 

 hand. It is the highest compliment we can pay him to say that such an achievement was not too much to expect from him. 



[These conclusions are fully substantiated by the interesting documents lately published by Mr Muirhead in the Correspondence 

 of Watt on the Composition of Water, p. 6, and in his Mechanical Inventions of James Watt, vol. i., p. Ixxxi. ; vol. ii. pp. 116, 118, 

 119, 275. In the last-cited passage Watt himself fixes the date and manner of his receiving from Dr Black his knowledge of the 

 doctrine of Latent Heat. He says, " I myself never attended his (Dr Black's) lectures; but the doctor explained his doctrines 

 to me about the year 1763."] Note added during printing. 



6 See Mr Watt's own narrative in Hobison's Mechanical Philosophy, ii., 113, note; and in Mr Muirhead 's Mechanical Inventiotu 

 of James Watt, vol. i. 



