I 429 ] 



Fourth, 



Barometer 30,05, what is the length of a vertical column 

 of air that weighs as much as 7^ of an inch of mercury ? 



Here 30,05—0,1=29,95. Then log. 3005=47784+ 



Log. 2995=476397 



Length = 1447 fathomi. 



Fifth. 



Barometer 28,77, (which is its mean height at Geneva) 

 what is the length of a vertical column of air that pofleffes the 

 above-mentioned weight ? 



Here 28,77 — 0,1 = 28,67. Then log. 28,77 = 458940 



Log. 2867 = 457428 



Length = 15,12 fathom- 



Hence they breath, at a mean, lighter air than we do in Dub- 

 lin, in the ratio of 141 2 to 1450, at the temperature of 32B, 

 and alfo drier. 



Vol. Vlli. 3H Sixth. 



