Cuap, IV,, § 1.] 
andconnee- mistry and Natural Philosophy (Dr Black and Dr 
tion with 
Dr Black. 
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 ;??! 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. 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.® Yet this experiment 
was not published until 1770,‘ 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 
MECHANICS.—WATT. 
867 
most cautious and accomplished of inductive philo- 
sophers.> Watt’s eminent merits, and doubtless his 
merits alone, gained him this happy position ; but 
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. 
well typified by his position in Glasgow. 
“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- 
His place in science was His posi- 
His was tion in 
(319.) 
casion of Watt’s improvements was the commercial Watt’s first 
consideration of economy. 
In 1763 or 1764, being 
experi- 
ments on 
called on to repair a model of 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.‘ 
mentality of his mother’s kinsman Mr George Muirhead, who had then (1754) just exch 
ged the prof ship 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. 
2 Robison’s Mechanical’ Philosophy, ii., 115, note (by Mr Watt). 
3 Ibid., p. vii., and 114, note. 
i 
4 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. 
5 It is perhaps unfortunate that Mr Watt, when on the verge of fourscore, contrary to his own intentions, but yielding to “ 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 
Wati’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 loss to understand how much cold water could be heated by so small a quantity in the 
form of steam,” he “applied to Dr Black, 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. 1xxxi.; 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 Robison’s Mechanical Philosophy, ii., 113, note; and in Mr Muirhead’s Mechanical Inventions 
of James Watt, vol. i. : 
