616 



STATE BOARD OF AGRICULTURE. 



is not comparable either witliin the same soil or in different soil types, 

 because the length of time and degree of freezing or super-freezing 

 were not the same neither within the same soil nor in the different soils. 

 These results are intended to show only that successive freezings tend 

 to decrease the lowering of the freezing point of some soils and not 

 of othei'S. 



Table 0. Decrease of the Lowering of llie Freezing Point with Successive Freezings. 



It will be noticed that the lowering of the freezing point of quartz 

 sand, burned silicic acid, and kaolin remains practically the same with 

 successive freezings, but that of sandy loam, Clyde loam, and the two 

 claj's, becomes less with each repeated freezing and that the degree of 

 diminution is very considerable, amounting in the clay soils to about 

 50% and in the sandy soil about 20%. This amount of decrease in de- 

 pression, hoAvever, in the clays, loams, etc., would not have been so great 

 had these soils not been cooled 3 or 4°C after they were frozen and kept 

 at that low temperature for some length of time. The decrease has 

 about reached its limit with all these soils as further freezings did not 

 cause any important variations. 



The question now is what causes this diminution of the lowering of 

 the freezing point with successive freezings in the case of the agricul- 



