[ 3S5 1 



e H A P. 



III. 



Of the Temperature of the Atmofphere,- 



Section I. 



Of the Temperature of the Summer Month's. 



That the heat of the atmofphere is derived, not from the im- 

 mediate adion of the folar rays that traverfe it, but from the 

 warmer and more fohd bodies with which it is or has been in 

 contadt, is a fatl which at prefent can admit of no difpute. I 

 have fufpended a thermometer and a feather about an inch over 

 the focus of a moft powerful burning lens, without producing the 

 flighteft increafe of heat in the one or of motion in the other. 

 H-ence it is plain the air was no way afFeded by it. That the 

 heat communicated to the atmofphere is in general gradually di- 

 minifhed in fome proportion during its progrefs upwards, at leafl; 

 in fummer, is alfo a fa£l fufKciently afcertained by the teftimony 

 of thofe who have afcended to great heights, either on mountains 

 or in baloons. But the ratijo in which heat is diminifhed in its 

 progrefs upwards, has been varioufly ftated, and the means by 

 which this diminution is efFeded, appear to me to have been in* 

 corredly determined. 



EULER 



