128 OUTLINES OF FORESTRY. 



same quantity of the sun's heat falling on an equal 

 area of bare ground. Therefore, the sun's heat 

 when permitted to fall on a forest region is more 

 thoroughly absorbed, is spread over a greater sur- 

 face, and penetrates the ground more thoroughly 

 than it would if thrown on bare ground. For, 

 when the rays fall on a bare, dry, parched surface, 

 they penetrate the ground to but a small depth, 

 and heating a smaller amount, must necessarily 

 produce a greater increase of temperature. 



The same is true as regards the loss of heat: 

 forest districts, which take in heat slowly, part 

 with it slowly; while bare, uncovered surfaces, 

 which take in heat quickly, part with it quickly. 



It, therefore, follows that since the forests do not 

 rapidly heat, they do not become excessively hot 

 in summer; and, since they part with their heat 

 slowly, they do not become very cold in winter. 



The fact that an area covered with forests does 

 not tend to become as cold in winter as bare, 

 uncovered ground, exerts a great influence on the 

 depth to which the frost extends downwards. 



The non-conducting power for heat of even a 

 very thin layer of snow is well known. If snow 

 falls before the frost penetrates the ground to any 

 great depth, it will act as a covering to prevent the 



