130 



MATHEMATICAL AND PHYSICAL SCIENCE. 



[Diss. VI. 



(591.) 



friend 

 his theory 

 of rain and 

 vapour 



make the requisite experiments. So cool a tempera- 

 ment was not likely to grow warmer as age advanced. 

 Almost as indifferent to the honours of discovery as 

 his stoical contemporary Cavendish, unlike him he 

 enjoyed in a high degree intercourse with the conge- 

 nial society which Edinburgh at that time afforded. 

 He loved to converse infinitely better than to write ; 

 especially when he could converse intimately with 

 such men as Adam Smith, David Hume, Adam Fer- 

 guson, Principal Robertson, Dr John Robison, John 

 Home, Clerk of Eldin, and Dr James Hutton. 



HUTTON was perhaps Black's dearest friend, and 

 Dr ^ u " on may be mentioned here (episodically) as no ordinary 

 intimate thinker in Natural Philosophy, as well as in Geology 

 and Metaphysics. Besides the " theory of the Earth," 

 !?_^ or 'j wn ich will ever bear his name, and which, after va- 

 rious transmutations in name and form, is now by 

 far the most widely prevalent, his theory of Rain 

 was an ingenious and important speculation. Other 

 branches of Meteorology also claimed his attention, 

 particularly, as might have been expected, those 

 which are connected with the temperature of the 

 earth. He was one of the first who drew conclu- 

 sions from the temperature of springs, with regard to 

 change of climate due either to increased latitude or 

 to increased height above the sea. His hygrometer, 

 in which the dampness of the air was estimated 

 by the coolness due to evaporation, was unquestion- 

 ably the first suggestion of a method now in general 

 use. His ideas on the constitution of matter were 

 bold and ingenious, though not on all points tenable. 

 They resembled those of Boscovich, though inde- 

 pendent of them. He published a voluminous trea- 

 tise on several subjects in Natural Philosophy, and 

 a still more formidable one on the Principles of 

 Knowledge, neither of which attracted much at- 

 tention at the time, and have been long forgotten ; 

 yet it is not unlikely that some of his speculations 

 in metaphysics might be worth the labour of re- 



examination. His friend and commentator, Playfair, 

 (whose style was as remarkable for perspicuity as Dr 

 Hutton's was the contrary) has drawn the following 

 lively contrast between the characters of Hutton and 

 Black, which may properly conclude this notice : 

 " Ardour and even enthusiasm in the pursuit of Contrast 



science, great rapidity of thought, and much anima- of Black 

 ,. ,'.*. . , v 3 V, TT , and Hut- 



tion distinguished Dr Hutton on all occasions. ton 



Great caution in his reasonings, and a coolness of 

 head which even approached to indifference, were 

 characteristic of Dr Black. On attending to their 

 conversation, and the way in which they treated any 

 question of science and philosophy, one would say 

 that Dr Black dreaded nothing so much as error, 

 and that Dr Hutton dreaded nothing so much as ig- 

 norance ; that the one was always afraid of going 

 beyond the truth, and the other of not reaching it. 

 The curiosity of the latter was by much the more easily 

 awakened, and its impulse most powerful and imperi- 

 ous. With the former, it was a desire which he could 

 suspend and lay asleep for a time; with the other, it was 

 an appetite that might be satisfied for a moment, but 

 was soon to be quickly renewed. . . . . Each 

 had something to give which the other was in want 

 of. Dr Black derived great amusement from the vi- 

 vacity of his friend, the sallies of his wit, the glow 

 and original turn of his expression ; and that calm- 

 ness and serenity of mind which, even in a man of 

 genius, may border on languor and monotony, re- 

 ceived a pleasing impulse by sympathy with more 

 powerful emotions." 1 



Black died on the 6th December 1799. 2 His death, (592.) 

 as recorded by his kinsman, Adam Ferguson, 3 was Black's 

 one of the most touching on record. It succeeded his death - 

 customary state of health by an interval inappre- 

 ciably short, and, as appeared by the accompanying 

 circumstances, without the slightest physical emotion. 

 The philosophic composure of his whole life was mir- 

 rored in the serenity of its close. 



2. CAVENDISH. 4 His Singular Character and Attainments Eminent Chemical Discoveries 

 Observations on Heat and on other Branches of Physics LAVOISIER The Calorimeter 

 Theory of Combustion and of Oxidation. 



Cuvier has justly remarked, in his biography of 

 (593.) Cavendish, that he had to struggle in his scientific 

 Cavendish. career a g a i ns t obstacles much more rarely encoun- 

 tered, and perhaps less easily overcome, than those 



which beset the progress of genius cramped by poverty 

 and neglect. Cavendish was the descendant of one 

 of England's noblest families, and he was likewise 

 the possessor of enormous wealth ; yet neither of 



1 Playfair's Biographical Account of Dr James Hutton, Works, vol. iv. 



8 Muirhead's Correspondence of James Watt. Introd., p. xxii. 3 Preface to Black's Lectures, by Robison, p. Ixxiv. 



4 I find an apology almost necessary for introducing at some length the biography of Cavendish into a chapter professedly on 

 Heat, his positive discoveries connected with which were less notable than in some other departments. But besides that his posi- 

 tion in the first rank of chemists naturally indicates his place to be between Black and Dalton, I felt a wish to bring out the 

 relief of the striking intellectual characteristics of those three remarkable men, by placing them in juxtaposition. I may add 

 that these three sections were the earliest written of this Dissertation, at a time when I had hoped to interweave into its compo- 

 sition more of the purely biographical character of each period of scientific history than I found it afterwards practicable in all 

 instances to carry out. I trust, however, that it may be found a not unwelcome variety amidst the abstruser details of science. 

 In the case of Cavendish, too, so various are his claims on our notice, that it was inevitable to recur to tbetn in different chap- 

 ters, especially 'in those on Astronomy and Electricity. It was not, therefore, really material under which head the more strictly 

 personal details were given to which I have alluded. 



