[ 463 ] 



Thus fuppofing the length of the vertical column icoo feet, the 

 weight of thefe loco fee: will be greater when the barometer below 

 {lands at 30 inches, than when it flood at 29 inches, and confe- 

 quently the height of the barometer to which they are fubjedl will 

 be proportionably diminifhed — Thus in temperature 3c'', baro- 

 meter 30, a'vertical column of air of roco feet in length, that is 

 83 3333 feet or 13,888 fathom, weighs 3:8,8 grains, for logarithm 

 30=4771,^13 13,888 fathoms gives the log. 4757325, which cor- 

 refponds with the natural number 29,90+5 inches. And 30,0000 



Inches Inches. 



inches — 29,9045= ,0955 and ,0955 of an inch of mercury = 

 3443,2 grains X ,0955 = 328,8 grains. — But when the barometer 

 below is at 29 a vertical column of 1000 inches will be found 

 by a fimilar procefs to weigh 317,9 grains, the upper barometer 

 being 28,90772. 



3 M 2 Table 



