Variation of Temperature, Sec. in the Atmosphere* 169 



sound not yet published, with which the author has kindly 

 favoured me, it appears Moll's late experiments, reduced to 

 dry air at 32°, give 1089.4 feet, the same as our theory. In 

 the same article, some of Goldingham's experiments at Madras, 

 when reduced to 32o, it seems make 1089.9 ; the mean of his 

 other experiments differing us much as 10 feet. 

 Collecting these observations together, we have — 



Diff. Feet. 

 —2.5 



— 1.9 

 + 1.1 

 + 3.1 

 + 0.0 



— 0.5 



+ 0.12 



I have no more time to devote to this part of the communi- 

 cation, than just to notice the extreme minuteness of the mean 

 difference of our theory, only 1^ inch, compared with that of 

 the old, amounting to 53 metres, or 174 feet. Laplace has, 

 indeed, contrived to reduce this difference to 13 or 14 feet, by 

 an ingenious, but very questionable, hypothetical assumption. 

 The theory from which I have deduced the preceding formula 

 requires no such assistance ; nor 1 believe any thing beyond 

 the simple definition of an air. 



II. — Diminution of Temperature. 



Let us now turn our attention to the other formulae. Sup- 

 posing/the Fahr. temp, at the higher station, F being that at 

 the lower, and substituting for S and s their values in (2) and 

 (3), we get 



..{L_(|y}.lM^iia.326.>2«,e5{,-(£)*l. 



(/+448)-:„dP-/=2J = 5i.„.„„. j^^ 



From the latter of these theorems it appears that the Fahr. 

 temp, decreases uniformly at the rate of 1° for every 326^ feet. 



* These computations, and those that follow, are extracted from a letter in which 

 the metre was reckoned to be 3.281 Eng. feet. 



