[ ASo ] 



To prove the fitnefs of this coefficient it is neceffary to give 

 fome inftances of barometrical menfuration, wherein it is juftified 

 by refults nearly agreeing with geometrical menfuration. 



Barometrical menfuration is founded on this principle, that 

 the denfity of the atmofphere and the height of mercury in a 

 barometer deereaje in a geometrical progreiTion, correfponding wilh 

 an increaftng arithmetical progreffion as wc afcend into the atmof- 

 phere ; though it is only in the mean temperature of 32° that 

 -this geometrical progreffion can be truly indicated in Englifh 

 meafures. The method therefore followed is, after equating both 

 barometrical heights fo far as thefe heights are occafioned by dif- 

 ference of temperature*. 



10. To deduce from the correded difference of the logarithms 

 the heights refulting from the geometrical progreffion, as ffiewn, 

 p. 439. This is called the Logarithmic refiilt. 



And 2dly, as this height is always inferior to the real height 

 when the mean temperature (^f the atmofphere furpafles 32°, to 

 add to the logarithmic refult, the quantity which that column of 

 air ^'ains in confequence of its mean temperature being fome 



degrees 



* The moft convenient mode of correflion is fhevrti, p 438. 



