108 



THE PRINCIPLES OF SOIL MANAGEMENT 



45. Formation of ice crystals. As will be seen in 

 the consideration of soil moisture, the water is distrib- 

 uted in the fine pores in the soil. When it freezes, 

 it crystallizes in long needle-like crystals. The crystal- 

 lizing force seems to be considerable. In freezing, the 

 crystals gradually grow first in the larger spaces. There 



is a marked with- 

 drawal of mois- 

 ture from the 

 smallest spaces 

 to build up the 

 ice crystals in 

 the large spaces. 

 The soil mass is 

 separated by the 

 crystal, and the 

 result of a single 

 hard freeze of a 

 wet soil is to 

 shatter it into 

 pieces. And the 

 repetition of this 

 process by sub- 

 sequent freezing 

 further breaks up 

 the soil, that is, 

 it creates new 

 lines of weak- 

 ness. This weak- 



Fig. 31. Ice crystals formed on the surface of i 



a heavy clay soil. These crystals are very effective neSS IS SllOWU 



in breaking up the soil and promote the process of i ,i j n 



granulation. by the following 



