218 ESSAY 



particles are to be seen, by means of the sun's 

 light, in the air over the middle of the Atlantic 

 ocean. These particles then must receive heat 

 from the sunbeams, which impinge upon them, 

 and this they will communicate to the con- 

 tiguous pellucid air. 



4. Unless it be admitted, that the atmosphere 

 is capable of intercepting part of the heat, 

 which is radiated into it by the sun, and of 

 converting this into heat of temperature, I deem 

 it impossible to find a sufficient reason, for the 

 great warmth which exists, after a long calm, 

 in air incumbent upon the Atlantic and Pacific 

 oceans, at the distance of a thousand miles or 

 more from any considerable body of land. It 

 cannot be derived from the neighbouring water, 

 since this is colder than the lower atmosphere ; 

 and no one will suppose it to be the same heat, 

 which the air had acquired from the last con- 

 tinent it had passed over, many days before. 

 But, if even this were supposed, another difc 

 ficulty would remain to be removed, which is, 

 that, during the whole of the calm, the air is 

 cooled every night, and again becomes warm 

 in the day *. 



* One reason is hence apparent for the great coldness of 

 the high regions of the atmosphere ; since the air in them 

 must be less fit, than that of the lower strata, to arrest heat 

 which is radiated into it. 



