Biographical Memoir of' Henry Cavendish. %i\ 



only give estimation to those possessed of them, in so far as they 

 are sustained by talent. It is therefore necessary to prepare the 

 young nobility for business by a liberal education ; and among 

 so many youths whose minds have been stored with useful 

 knowledge, there are always found some wlio prefer devot- 

 ing their energies to the research of eternal truths, than in pur- 

 suing interests of the moment. Mr Cavendish, throughout 

 tfce wlwJe of his life, shewed that this preference was the result 

 of a natural taste ; but it was necessary for him that it should 

 be confirmed at an early age by domestic examples. Lord 

 Charles, his father, was also fond of science, and has left good 

 observations in natural philosophy. It is probable that he 

 directed the early studies of his son ; although we have no infor- 

 mation respecting the method which he followed in educating 

 him, nor even of the first attempt of the young Henry in the 

 carcCT of science. He appeared suddenly in it, but in such a 

 manner, as to shew that it was already familiar to him. The 

 first step which he made, opened up a path before unknown, 

 and gave the signal of a new epoch. We allude to the Memoir 

 on Airs, which he presented to tlie Royal Society in 1766*; 

 and in which he aimed at nothing less than the establishment 

 of these propositions, till then unheard of : Air is not an de- 

 ment ; there exist several kinds of air essentially different. 



From the time of Van Helmont, philosophers knew that vari- 

 ous bodies exhale fluids, which resemble air in their permanent 

 elasticity. Boyle discovered at an early period, that they are 

 unfit for respiration ; Hales conceived the means of measuring 

 them ; Brownrigg and Venel shewed that the sharp taste of 

 certain mineral waters is owing to them ; Black discovered, that 

 it is by their presence that limestone is distinguished from quick- 

 lime, and the common alkalies from caustic alkali ; lastly, Mac^ 

 bride directed the attention of medical men to them, by employ- 

 ing them against putrefaction. But tlieir various kinds had not 

 been distinguished with sufficient accuracy ; it was not generally 

 believed that they were specifically different ; and more tlian one 

 j^ilosopher of celebrity always maintained, that these varieties 

 were nothing but common air altered by the emanations of the 



• Pba. Trans. IT6«. P. 141. 



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