Mr Forbes on Polar Temperature. 17 



Art. II. — Observations respecting Professor Leslie^s For- 

 mula for the Decrease of Heat in the Atmosphere ; and his 

 Opinions respecting the Polar Temperature. By James D. 

 Forbes, Esq. F. R. S. Ed. Communicated by the Author. 



My Dear Sir, 

 As I know that in every question of literary justice, nunquam 

 sero is your motto, I cannot help drawing your attention to an 

 article which appeared some years since in your Journal, com- 

 municated by an anonymous correspondent. It is in No. ix. 

 First Series, and has for title, " Demonstration of Professor 

 Leslie's Formula for determining the decrease of Heat depend- 

 ing on the Altitude, without ' a delicate and patient research.' " 

 It is only very x-ecently that, having paid attention to this very 

 curious subject, I have been led to examine every statement 

 connected with it which came under my observation. Now 

 the article to which I allude excited my particular attention, 

 and the result of my inquiries into the merits of the case was, 

 that the author of it must, to say the least, have been very 

 imperfectly acquainted with what had been done on the sub- 

 ject. His demonstration amounts merely to this, that, from 

 the ordinary logarithmic formula, he undertakes to give one 

 which shall be identical with the law of uniform decrease of 

 temperature, at the rate of l°Cent. for 81 fathoms of altitude. 

 To do this would indeed have been a small boon to science, 

 and we might certainly have expected, that, instead of confin- 

 ing himself to the undemonstrated enunciation contained in 

 Professor Leslie's Elements of Geometry, he would have con- 

 sulted the article Climate, in the Supplement to the Encyclo- 

 paedia Britannica, which was even then published some years, 

 where he would have discovered, that the " delicate and patient 

 research" alluded to was of an experimental kind, and so de- 

 serving of that appellation, that, from the very refined nature 

 of the experiments, (which were instituted to determine the 

 capacity of air of different degrees of density for heat,) few 

 philosophers have been disposed to place the same confidence 

 in the deductions to which they lead, as the Professor himself 

 has done. Indeed, previous to the appearance of the article 

 before us, a highly distinguished philosopher had expressed his 



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