Daniell on a new Hygrometer, 126 



beaucoup. II faut toujours faire iine experience avec celui de 

 I'auteur lorsqu'on veut connoitre I'etat hygrometrique de I'air ; 

 il faut uen provision d'ether, etc. Avec celui de De Saussure, 

 au contraire, il suffit de le regarder, en observant aussi le 

 thermom^tre, dont les indications doivent toujours marcher 

 pareilic telment h celles de Thygrom^tre, ainsi que I'a prescrit 

 soigneusement I'auteur dans son Essai sur THygrometrie, I'un 

 des fruits les plus remarquables de sa sagacite et de son genie." 

 Strange, indeed, would it have been, had the presumption 

 been correct, that I was totally unacquainted with the instru- 

 ment invented by the illustrious countryman of my annotators. 

 Long have I been an humble admirer of his sagacity and 

 genius ; and to no work have I been more indebted for useful 

 instruction on the subject on which it treats, than to the 

 essay above referred to. My reason for not making mention of 

 the hair hygrometer of De Saussure, was the conviction on my 

 mind of the general admission of the inadequacy of any known 

 application of the hygroscopic properties of animal or vegetable 

 bodies, whether hair, whalebone, or rat's bladders, to measure 

 the absolute quantity of vapour at any time existing in the at- 

 mosphere. I had selected one as the best contrivance of this 

 nature to elucidate this point, by contemporaneous observations 

 with ray own instrument ; and the editors of the Bibliotheque 

 Universelle themselves, in recording my opinion, ** on verra 

 combien ses indications sont vagues et peu concluantes," add, 

 *' Nous ne sommes pas tres eloignes de cette opinion." Now, 

 I must own that I am quite at a loss to conceive any objection 

 that can apply to the whalebone that does not equally affect the 

 hair, as a measure of vapour. But I shall prefer supporting this 

 conclusion by the authority. of others, rather than by any argu- 

 ments of my own, especially as I think that I can produce autho- 

 rity which the candour of the editors themselves will allow to be 

 conclusive. M. De Humboldt, the celebrated philosopher and 

 traveller, who is equally distinguished by his accuracy of obser- 

 vation, and by his philosophic generalizations, and who has had 

 opportunities of making observations upon this subject which 

 no other person ever yet enjoyed, and no other ever was more 



