XIII. Observations on the Mean Temperature of the Globe. 

 By David Brewster, LL. D. F. R. S. Lond. & 

 Sec. R. S. Edin. 



(Read February 7. 1820 J 



XF no provision has been made by the Great Author of Na«- 

 ture, for equalising the light and heat projected upon the dif- 

 ferent bodies of our system, we may consider the earth as re- 

 ceiving, from the direct action of the solar rays, a degree of 

 heat, intermediate between the condensed radiations sustained 

 by Mercury and Venus, and the attenuated warmth which 

 reaches the remoter planets. The heat which our Globe thus 

 acquires from its locality in the system, is again tempered by 

 the obliquity of its axis, and is distributed over the same pa- 

 rallels of latitude by its daily rotation. When the Sun is in 

 the Equator, his rays, beating on the Earth with a vertical in- 

 fluence, impart to it the full measure of their action ; and as 

 his meridian altitude decreases, their intensity suffers a corre- 

 sponding diminution. The burning heat at the Equator be- 

 comes moderated in higher latitudes. In passing through the 

 temperate zone, it declines with great rapidity, and between 

 the Arctic Circle and the Pole, the rays of the Sun are unable 

 even to temper the piercing cold which reigns in these inhos- 

 pitable regions. 



vol. ix. p. i. c c This 



