PRIMER OF PRIMERS. 199 



therefore, tend to prevent sudden changes in the 

 climate. 



A bare, uncovered area, such as a desert, is sub- 

 ject to sudden changes in its climate. 



The climate produced by an extended land area 

 is called a continental climate; that produced by 

 an extended water area, an oceanic climate. A 

 continental climate is characterized by great and 

 sudden changes of temperature; an oceanic 

 climate, by a comparatively uniform temperature. 

 The forests tend to produce a climate characterized 

 by a comparatively uniform temperature. In this 

 respect, therefore, the forest climate is like the 

 oceanic climate. 



The sun does not heat an area covered by forests 

 either as intensely or as rapidly as a bare area, 

 because : 



1. The heat is spread over the greatly-extended 

 surfaces formed by the trees of the forest and its 

 underbrush. 



2. The vegetable covering acts as a screen to 

 protect the ground from the direct action of the 

 sun's rays. 



3. The air over the forest is moister than that 

 over the fields, and this moist air acts either as a 

 screen to protect it from the heat of the sun, 



