Biographical Memoir of Sir John Leslie. 1 



tion, which Mas partly intended to promote the circulation of 

 his Instruments, and to explain their principles, would have 

 been infinitely more useful had its author superadded the 

 powers of methodical and elementary exposition to his other 

 high endowments. But, notwithstanding its defects, in these 

 particulars, it was much commended by those competent to ap- 

 preciate its value as a contribution to science.* Closely con- 

 nected with the subject of this treatise, and which we may 

 therefore notice here, though it did not appear till some years 

 later, was an ingenious Paper, published in 1818, in the Trans- 

 actions of the Royal Society of Edinburgh, under this title : 

 On certain impressions of cold transmitted from the higher atmo- 

 sphere ; with a description of an Instrument adapted to measiire 

 them. The ^thrioscope, the instrument here alluded to, is, 

 in another place, described, in the poetical language of its au- 

 thor, as " fitted to extend its sensation through indefinite space, 

 and to reveal the condition of the remotest atmosphere." 



In the autumn of 1814, Professor Leslie indulged himself 

 mth a tour of six weeks in France and the Netherlands. He 

 never was satisfied if he allowed a vacation to pass without 

 visiting some foreign scenes. One or two extracts from let- 

 ters written by him on the present occasion, may be here in- 

 troduced, as either curious in themselves, or characteristic of 

 the writer. Writing from Paris, on the 1st of August, he says, 

 " You know that it was not my intention at present to mix 

 much with the S^avans. But I have been so well received, 

 and even feasted by them, that I may perhaps depart a little 

 from my original design. Humboldt has been very kind and 

 attentive to me, and introduces me wherever I want. They 

 are much better acquainted with what we are doing than I 

 should have imagined. My book on Heat is better known 

 than in England. I was even reminded of some passages in it 

 which in England were considered as faiociful, but which the 



" See Edinburgh Review, vol. xxiv. \). 339-52 ; and Dr Thomson's Annals 

 of Philosophy, vol. ii. p. 457-C2, for a skilful analysis of the treatise. In the 

 trial above alluded to, the party prosecuted took an Issue to shew, that the 

 above article in the Edinburgh Hevieio, in commendation of the work, was writ- 

 ten by Mr Leslie himself! The attempt was not made; and it is hardly 

 worth while to mention, with reference to such a charge, that the article was 

 written by that very able chemist, the late Dr John Murray. 

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