STUDY X. 8 I 



yt the Sun, becaufe it fends them back without 

 any tint, as pure as it receives them ; and that 

 black, on the contrary, is the lead adapted to their 

 reflection, becaufe it abforbs them. This is the 

 reafon why gardeners whiten the walls againft 

 which their efpaliers are planted, in order to acce- 

 lerate the maturity of their fruits, by the reverbe- 

 ration of the Sun's rays; and why opticians blacken 

 the walls of the camera-obfcura^ that their reflexes 

 may not difturb the luminous picture on the 

 tablet. 



Nature, of confequence, frequently employs to 

 the North the white colour, in order to increafe 

 the light and heat of the Sun. Moll of the lands 

 there are whitifh, or of a clear gray. The rocks 

 and fands of northern regions are filled with mica 

 and fpecular particles. Farther, the whitenefs of 

 the fnows, which cover them in Winter, and the 

 vitreous and cryftalline particles of their ices, are 

 exceedingly adapted to mitigate the action of the 

 cold, by reflecting the light and heat in the moft 

 advantageous manner. The trunks of the birch- 

 trees, of which the greateft part of their forefts 

 confift, are covered with a bark as white as paper. 

 Nay, in fome places, the earth is clothed with a 

 vegetation completely white. 



VOL. III. g " In 



