78 AGRICULTURE 



the soil, with the accompanying increase in 

 volume that always accompanied such a 

 change. That the surface of the ground is 

 raised during the continuance of frost is 

 convincingly shown by the fact that field 

 gates and garden doors, which usually swing 

 quite freely, may become firmly fixed to the 

 soil. When ground is heaved up by frost 

 the plants are raised with it, and when the 

 ice is converted into water the plants tend 

 to sink back to their original position, but 

 their roots never quite attain to the level 

 from which they started. If this process 

 of heaving-up under the influence of frost is 

 frequently repeated during winter, the plants 

 may be left entirely exposed on the surface 

 of the ground, no part of their roots being 

 retained below the surface. It follows, 

 therefore, that the worst type of weather 

 conditions, from this point of view, is that 

 which is associated with frequent alternations 

 ^between frost and fresh, which, continued 

 throughout a winter, will produce much more 

 disastrous results than a long-continued 

 frost, with the temperature at a lower range. 

 It is a matter of experience that the 

 process of drainage is associated with earlier 

 harvests, a result due to the fact that dry 

 land can not only be sowed earlier, but, 



