Of BAROMETRICAL MEASUREMENTS. 113 



nz / r 



r-H ( ~~H-3 



_)(! i) \ (i m y 



2 * , 



fa *'(-*) 



qs(H- 



. / H-r 



O <y O 9* \ 77^ / * v 



-&/O -i"^ \ * / / T * M ^ 



-A) 



r 



. THE value of z is to be found from this equation ; and as* 

 the firft ftep in the approximation, we may fuppofe s fo great in 

 refpedl of a, that s+z =. s, nearly j and, alfo, that all the 

 terms divided by s vanifh ; which, in fadl, is the fame thing with, 

 fuppofing the force of gravity to be uniform. We have, then, 







*y ~ . \~ 



z ^-7 T- 



(i m) (i my 



28. THIS is the exac~l value of z, on the fuppofition that gra- 

 vity is uniform, and that the elafticity of the air is. not fimply 



as its denfity, but as the power of it denoted by . But 



. r . I +" 



if we content ourfelves with an approximation, which the 



finallnefs of n renders eafy, the logarithms of b and (3 mav be 



introduced, 



