Nov. 15, 1920 Temperature Which Soils Can Reach without Freezing 269 



No definite explanation can be offered for this phenomenon. It 

 would appear, however, that the true explanation is to be found in the 

 difference in the size of particles of the two classes of materials. The 

 artificial materials possess, of course, incomparably finer-sized particles 

 than the soils do, and it would seem that when the division of a substance 

 approaches the molecular state it ought not to affect the freezing of water 

 materially. However, in a series of experiments conducted to ascertain 

 if clay soils could withstand a greater degree of supercooling than coarse 

 sands, it was found that sands with infinitely larger-sized particles re- 

 sisted freezing equally as well as clays. It is possible, therefore, that 

 other factors, such as the nature of the material, its cohesive and ad- 

 hesive properties, its specific gravity, etc., also come into play in affect- 

 ing the degree of supercooling. 



In order to ascertain if the degree of moisture content exerts any 

 influence upon the resistance of soils to freezing, different water contents 

 were employed in all the various soils. The results failed to show, 

 however, that moisture had any appreciable influence on the resistance 

 of soils to freezing. Soils at a very low moisture content could not be 

 supercooled any further than at a very high moisture content. 



The foregoing experimental results afford a new and significant in- 

 sight into the temperature of soils during the cold seasons. In the first 

 place, they go to show that mineral soils may be cooled down to -4.2 C. 

 (7. 54 F.) and peats and mucks down to -5 C. (9 F.) without freez- 

 ing. This being the case, the conclusion naturally follows that during 

 mild winters and in mild climates in the winter the soils may not freeze 

 even though they are cooled below their freezing point. 



In the second place these findings prove quite conclusively that the 

 method now in vogue for measuring temperature in soils in cold seasons 

 may not give entirely the true facts. The thermometers will be re- 

 cording the temperature to be several degrees below the freezing point 

 and yet the soils may not be actually frozen. 



The foregoing experimental results are very significant from still 

 another standpoint. As it is well known, water in the liquid state has 

 twice the specific heat that ice has. As long as the soil moisture remains 

 in the liquid state the temperature fluctuations in the soil will be corres- 

 pondingly slower and smaller. 



Indeed, the ability of soils to resist freezing even when their tem- 

 perature is much below the freezing point throws considerable new 

 light on questions regarding the temperature of soils in cold seasons and 

 consequently upon the physical, chemical, and bacteriological pro- 

 cesses going on in the soils during those seasons. 



