216 Biographical Memoir of Henry Cavendish. 



rections made upon them by Fontana. Mr Cavendish, by a 

 slight difference in the manual process^ gave them a very supe- 

 rior precision *, and, having employed them for comparing air 

 taken in different places and at different times, arrived at the 

 unexpected result, that the portion of respirable air is the same 

 everywhere, and that the smells which so perceptibly affect 

 our senses, and the miasmata which so cruelly attack our 

 health, cannot be investigated by any chemical means — a result 

 which, although at first sight almost discouraging, presents an 

 immense perspective to the reflecting mind, and already shews 

 in the distance sciences which have not yet been called into 

 existence, and for which alone is perhaps reserved the secret 

 of those which we possess. M. de Humboldt has confirmed this 

 fact, in the most distant regions, by means of the inflammable 

 air eudiometer. MM. Biot and Gay-Lussac found it not less 

 true in the highest parts of the atmosphere which man has been 

 able to attain by means of the balloon, than in its lowest strata. 

 Thus it was still an agent discovered by Mr Cavendish, that 

 these adventurous philosophers employed to verify another of 

 his discoveries. 



Such are the labours that have assigned to Mr Cavendish 

 so distinguished a place among the cultivators of chemistry ; 

 they occupy but a few pages of print, yet they will survive many 

 large books; but we must not estimate the difficulties which 

 attended them by the space which they fill. To have untied 

 the secret knot that bound together so many complicated phe- 

 nomena, to have pursued the same principle through so many 

 windings and metamorphoses, and especially to have explain- 

 ed with such precision what had for ages eluded the most 

 expert philosophers was, in a few minutes, rendered evident to 

 every one, could be nothing but the eff*ect of meditations, not 

 only the best directed, but the most obstinately persevering. 

 Mr Cavendish was a living proof of the truth of the adage of 

 one of his most illustrious cotemporaries, that genius is but a 

 greater aptitude for patience ; a maxim strictly true, if we add 

 to it, that it must be the patience of a man of intellect. 



Another not less valuable quality which he possessed was his 

 severity in the matter of demonstration. Nothing doubtful was 



* Phil. Trans. 1783, Part I. p. 106, 



