at the Surface of the Earth. nt 



add a few observations of a more general nature, which tlic pre-' 

 ceding reasoning suggests with regard to the temperature of the 

 globe, and its relation to solar lieat. From the nature of the 

 Jigencj of the atmosphere in diffusing heat, the conclusions seem 

 to me almost necessarily to follow, — that there is a tendency to 

 equalization of temperature over the whole surface of the earth, 

 — that this continues to operate in sucli a manner, that in the 

 progress of time the dilTerencc at different parts must become 

 less than what existed at a preceding period ; and that, idti- 

 mately, a temperature nearly uniform shall be established over 

 the whole. 



At the hotter parts of the earth's surface, the temperature can- 

 not increase, or must increase very slowly, and to no grr^at ex- 

 tent ; for, if it were to rise higher, the ascent of heated air from 

 it, and the transfer of this to tlie colder jiarts of the surface, 

 would only become more rapid. But the temperature at the 

 colder regions may rise higher ; for the direct ascent of heated 

 air is there less aljundant, and wliat recedes in a lateral direction, 

 does so, deprived of caloric, which it has yielded to the earth. 

 "Whatever discharge of caloric, too, may take j)lace by radiation, 

 must be principally from the hotter parts of the surface; from' 

 the colder it nnist l)e much less considerable, for the quantity 

 radiated is less as the temperature is low : it increases, too, at a 

 higher rati6 than the increase of temperature; and hence, if 

 increased radiation from increased temperature did take place at 

 both, being greater at the former than at the latter, its effects 

 would be more considerable in retarding a further augmentation 

 of temperature. Thus it appears, that the causes counteracting 

 rise of temperature at the surface of the globe, act most power- 

 fully at those parts where it is high, and any progressive rise, 

 therefore, must be principally at tliose where it is low. 



The effect of this arrangement may be most obvious, perhaps, 

 from comparing the two extremes. At the equator, the ascending 

 current of warm air, carrying off heat, is constant or nearly so ; 

 towards the poles, the descending current imparting heat, must 

 be equally constant. The heat directly communicated at the 

 former by the solar rays, and the heat communicated at the lat- 

 ter by the current of warm air, will both be in part conveyed 

 through the solid mass towards the interior ; but this will alwavs 

 be with a decreasing temperature as it proceeds, — that is tosav, 

 the first or exterior layer will be at a higher temperature than 

 the second, the second than the third, and the accumulation, 

 therefore, will be at the surface, to a certain extent. At the 

 poles this may continue tfl proceed, because heat is there com- 

 municated without an equal abstraction. But at the equator it 



Vol . 1 G . No. 209. Sc[>t . 1815. M u i 11 



