at the Surface of the Earth. 1/3 



seems to be no discharge of radiant heat from the former ; and 

 still more, wlicn the temperature of the solid is lower than that 

 of the elastic medium, (and tliis is usually the case in colder re- 

 gions,) it is rather disposed to absorb than to emit caloric by 

 radiation. The resistance, too, opposed by the atmosphere to 

 the discharge of ravs having the weak projectile force which those 

 emitted at such a low temperature must have, would in a great 

 measure prevent their escape, if the power to radiate did actually 

 exist. 



At the hotter parts of the earth's surface there may be some 

 emission of caloric by radiation, but it is not difficult to show, 

 that the quantity of this cannot be equal to the quantity com- 

 municated by the solar rays; for of the heat derived from the 

 latter source, a portion is absorbed by the earth, and conveyed 

 to the interior, as is apparent from the decreasing temperature, 

 as wo recede from the surface to a certain depth ; and anotiier 

 portion is carried off by the ascending current of heated air, and 

 conveyed to colder regions, where it is also ab.sorbed. 



Thus, even from those parts of the surface of the earth where 

 the circumstances are those most favoural)le to radiation, the 

 quantity radiated cannot be equal to the quantity received by the 

 solar rays. Over the whole surface, the difference must be still 

 greater; and instead of the conclusion, that this planet discharges 

 an excess of heat by radiation, there is every reason to draw the 

 opposite conclusion, — that part of the heat which it receives 

 from the sun is retained. 



The only reason, at least, that would lead to hesitation in ad- 

 mitting this last inference, is a hypothetical one, — that it is in- 

 consistent with that jierfect arrangement, which Ave are disposed 

 to believe exists among all the heavenly bodies, whence the sta- 

 bility of the entire system is maintained, asul v.hence, therefore, 

 in relation to any communication of caloric among them, the 

 <iuantity radiated by each will, on the whole, be equal to what 

 it receives. This, whether we restrict the view to the different 

 j)Hrts of our solar system, or extend it even to the universe, is no 

 doubt the conclusion which the imagination is naturally disposed 

 to embrace, though it may not 1)C supj;orted on any decisive evi- 

 dence, or may even be in some measure a],parently in ojipositioij 

 to the fact. But to suppose that this planet discharges more 

 caloric than it receives, would be not only in opposition to evi- 

 dence, but in opposition to the very principle which alone leads 

 to the admission that the quantity discharged may be equal to 

 the quantity received. 



Concluding, then, as it appears to me may be strictlv inferred 

 from the preceding rxjasoning, that our earth does net discharge 

 caloric from its surface into the regions of space, or at least does 



nut 



