ON DEW, &c, 201 



from the earth. Agreeably to Mr. Six's ex- 

 periments, the atmosphere at the height of 220 

 feet is often, upon such nights, 10 warmer than 

 what it is 7 feet above the ground. If, there- 

 fore, I am able to show, as I expect I shall be 

 in the course of a few pages, that the air at the 

 smaller height becomes colder than that of the 

 greater, from its vicinity to the surface of the 

 earth, previously rendered cold by radiating its 

 heat to the heavens, it will follow, that these 

 10 must be added to the quantity of cold 

 already mentioned ; and, consequently, that a 

 body on the ground may become, at night, at 

 least 40 colder than the air two or three hun- 

 dred feet above it, by the radiation of its heat 

 to a clear sky. 



I shall add, with the greatest diffidence, a few 

 words upon a final cause of the radiation of heat 

 from the earth at night, and upon some of the 

 circumstances which modify its action, though 

 fully conscious of the danger of error, which is 

 always incurred in the attempt to appreciate 

 the works of our Creator. 



The "heat which is radiated by the sun to the 

 earth, if suffered to accumulate, would quickly 

 destroy the present constitution of our globe *. 

 This evil is prevented by the radiation of heat 



* Count Rumford says j ' ' May it not be by the action of 

 these [frigorific] rays, that our planet is cooled continually, 

 and enabled to preserve the same mean temperature for ages, 



