no 



PRINCIPLES OF AGRICULTURAL CHEMISTRY 



changes are slower and more restricted in depth. The tempera- 

 ture of the soil is influenced by its color, water content, location, 

 composition, etc. 



Location. The following figure illustrates the effect of location 

 upon the light and heat received by the soil from the sun. Let E 

 and F. represent two equal beams of sunlight, falling upon the 

 south (A B) and the north (C D) side of a hill. It is evident 



Fig. 31. The south side of a hill receives more heat than the north. 



that the ray F is distributed over more surface than the ray E and 

 that its heat has a greater area to warm. The soil on the north 

 side thus receives less heat than that on the south side. The 

 difference depends on the situation of the sun, and the inclination 

 of the hill. It is for this reason that the south sides of hills in 

 northern regions may be green with vegetation while the north 

 side is covered with snow. A wall or hedge, by protecting the 

 soil from wind, or by reflecting heat upon it, may cause the soil 

 to be warmer. Maligoti arid Durocher found the average soil 



