252 OUTLINES OF NATURAL PHILOSOPHY. 



Professor LESLIE, in the Notes on his Elements of 

 Geometry, p. 495. edit. 2d, has given a formula for 

 determining the temperature of any stratum of air 

 when the height of the mercury in the barometer 

 is given. The column of mercury at the lower of 

 two stations being b, and at the upper , the 

 diminution of heat, in centesimal degrees, is 



/ \ 



I - ^ 1 25. This seems to agree not ill with 



observation. 



344. If t be the temperature of the air in cente- 

 simal degrees, and b the height of the barometer 

 in inches ; the specific gravity of the mercury in 

 the barometer, is to the specific gravity of the air, 

 as 4342.944 x 72 (1 -f .004 t) to b ; or the specific 

 gravity of mercury being 1, the specific gravity of air 



, b 



72 X 4342.944 (1 -f .004 t) ' 



Suppose the barometer to be carried to any infinitely 



small height /, above the place where it was first 

 observed; and let the mercury sink by the small 



quantity b. Let the temperature be supposed to 

 remain the same. Then the rule, 342, gives ti=, 



10000 (1 + .004 t) log r ; or, taking the hy- 



b b 



perbolic, instead of the tabular logarithms, 



is 



