CHAP. VI., 2.] 



HEAT. CAVENDISH. 



131 



(594.) 

 is per- 

 nal his- 



ry. 



(595.) 

 .s won- 

 rful 

 nge of 

 .entific 

 lOwledge 



these powerful temptations could withdraw him even 

 for an hour from the course of study which he had 

 marked out ; and which constituted for him at once 

 labour and relaxation, the end of living, and almost 

 life itself. 



The Honourable Henry Cavendish, son of Lord 

 Charles and Lady Anne Cavendish, was born at Nice, 

 October 10, 1731. 1 He entered St Peter's College, 

 Cambridge, 24th November 1749, where he resided 

 during the usual terms for above three years, when 

 he ought naturally to have graduated, which, how- 

 ever, he never did. That he had pursued at least 

 his mathematical studies with ability and success is, 

 however, nearly certain from the firm hold which he 

 ever after retained of them. He joined the Royal 

 Society of London in 1760, and published his first 

 paper in their Transactions in 1766. From the time 

 of his leaving Cambridge for some years his personal 

 history is not known, though he probably resided in 

 London. 



The subsequent history of Cavendish is the history 

 of his studies and his discoveries. The latter were 

 published in concise memoirs, written with scrupulous 

 precision, and all printed in the Philosophical Trans- 

 actions. If collected (which they have not been) they 

 would fill but an insignificant volume, yet include all 

 the requisites to establish a first-rate reputation. His 

 studies no doubt were enormous, for they occupied 

 every disposable moment of a life prolonged almost 

 to fourscore. They may be guessed at (in addition 

 to the published results) from his manuscript remains, 

 a few of which have been edited recently, but the 

 larger part remains in manuscript in the possession of 

 his heirs. Few if any branches of exact science were 

 unfamiliar to him ; and his published papers include 

 astronomy, mechanics, electricity, heat, chemistry, 

 and meteorology, besides which he cultivated mathe- 

 matics and geology. His reputation is one of those 

 which may be called in a peculiar sense European or 

 universal, because it marked a great epoch in science 

 to which the publication of his writings materially 

 contributed. That epoch was when chemistry be- 

 came a science of weight and measure. Cavendish 

 was a weigher and measurer almost by nature, and 

 entirely so by habit. It appears from his note-books 

 that he took the most scrupulous pains to ascertain 

 and record the quantities of the ingredients employed 

 in every experiment, even though they might be im- 

 material to the result ; and his whole life was metho- 

 dical in the same proportion. The immense impor- 

 tance of Cavendish's labours to the progress of science 

 in his day is found in the unanimous testimony of 

 his contemporaries ; and notwithstanding the extreme 

 retirement in which he lived, and the rarity of his 

 appearances as an author, he was generally regarded 

 as perhaps the leading man of science in England of 



his day ; and his good opinion was considered by con- 

 temporary philosophers as their highest praise. Sir 

 Humphry Davy's opinion of him (recovered and 

 published by Dr Davy from a manuscript lecture) 

 represents that of such of his countrymen as were 

 qualified to form one, and the writer of it was 

 usually fastidious in his judgments of others : " It 

 may be said of Mr Cavendish, what can perhaps hardly 

 be said of any other person, that whatever he has 

 done has been perfect at the moment of its produc- 

 tion. His processes were all of a finished nature. 

 Executed by the hand of a master, they required no 

 correction ; and though many of them were per- 

 formed in the very infancy of chemical philosophy, 

 yet their accuracy and their beauty have remained 

 amidst the progress of discovery, and their merits have 

 been illustrated by discussion, and exalted by time." 



After this eulogium of so competent a judge, I (596.) 

 shall be satisfied by a simple enumeration of those Chemical 

 chemical discoveries which were the most splendid d ' s overi < 

 results of his career, but which hardly come within dish, 

 the immediate scope of this dissertation. To him we 

 are mainly or entirely indebted for the knowledge of 

 hydrogen as a distinct elastic fluid or gas ; of the 

 exact constitution of the atmosphere, and the won- 

 derful constancy of its ingredients ; of the composi- 

 tion of nitric acid ; and finally, according to the 

 opinion of most persons (at least till lately), of 

 the non-elementary nature of water, and of its 

 precise constituents. This last and crowning dis- 

 covery has indeed been contested, and made the sub- 

 ject of a prolonged and bitter scientific controversy, 

 which hardly could be said to exist until the con- 

 temporary generation who witnessed the facts, and 

 also the succeeding one, had passed away. For Caven- 

 dish received until his death, and for nearly thirty 

 years after, the unquestioned tribute of at least the 

 primary merit in so great a step in science. The 

 topics more peculiar to the present essay (sufficiently 

 extensive besides) enable us to dispense with the un- 

 welcome task of once more analyzing a controversy 

 purely personal, and which has almost filled volumes. 

 I shall content myself with stating two considera- 

 tions, which must have great weight in turning the 

 balance of the evidence (supposing it balanced) in 

 Cavendish's favour. The first is founded on the 

 behaviour of Watt himself; the second on the known 

 character of Cavendish. 



As to the former consideration, I would remark that (597.) 

 Watt withdrew the letter to Priestley which he had Contro- 

 submitted to the Royal Society and which contained y ers y on 



i i J , ., n \_ e discovery 



his views respecting the composition ot water, before of the co ^ 

 it had been read at the meetings of that body. 2 The position of 

 causes of this suppression are candidly stated by water. 

 Watt in a letter to Sir Joseph Banks, published by 

 Mr Muirhead, 3 in which he states that he " thought 



1 Life of Cavendish, by Dr George Wilson ; a valuable biography, which has been printed in the series of publications of the 

 " Cavendish Society," and thus unfortunately has had but a limited circulation. 



2 Correspondence on the Composition of Water, p. 30. 3 Ibid. p. 62. 



8 



