37© On the PROGRESS of HEAT, &fr. 



b — — Log b, and therefore (i 19.), a % ~ — -r = 



r \x ? ;j 3m r Logo 



(b-b + bzU >S b \ 

 -» V r J a*bz 



a 3 mr Log b = Jm? > henCC When Z 1S Ver ? 



fmall, h = T 



3m r 



22. Therefore when z, or the height above the furface is 

 fmall, h diminifhes in the fame proportion that the height in- 

 creafes, which is conformable to experience. 



In our climate, when 2 = 280 feet, a h X x 28 ° = i°; fo 



that the co-efficient 3 = — — , and therefore 



2,mr 280 



b = T |n, 



280 



When the conflant quantities are thus determined, the for- 

 mula agrees nearly with obfervation. In the rule for barome- 

 trical meafurements, it is implied, that the heat of the atmo- 

 fphere decraafes uniformly ; but the rate for each particular 

 cafe is determined by actual obfervation, or by thermometers 

 obferved at the top and bottom of the height to be meafured. 



XI. 



