502 



STATE BOARD OF AGRICULTURE. 



It will be evident that the results obtained in this way are qualitative 

 and relative. No attemj.-t was made to determine the heat conductivity 

 in these cores of soils quantitatively because of the many errors in- 

 volved as shown and enumerated by Patten; also because the quantita- 

 tive results would not have any more significance either from the 

 theoretical or practical point of view, as the state of the material ex- 

 perimented upon was unstable. The method adopted, however, appears 

 to have been satisfactory and accurate as the readings could be check- 

 ed within two to four minutes with the exception of the peat in which 

 case the time varied as much as 10 minutes. This discrepancy was 

 undoubtedly due to the fact that the temperature rose so slowly in this 

 soil that it was difficult to note at once the beginning of temperature 

 rise as easily as it was in the other soils. 



There was probably no loss of heat from the box as the walls were 

 over one inch thick and well paraffined. The room temperature also 

 remained quite constant throughout the duration of this series of ex- 

 periments. 



The results obtained by the foregoing procedure are shown below. 

 They represent the time that e]ai)sed from the time the soil box came 

 in contact with the source of heat until the time the mercury column 

 of the thermometer at 7 inches from the surface of the soil commencefl 

 to rise. The data for the other six thermometers for the first six inches 

 respectively, are left out for the sake of simplicity. The figures for all 

 soils are the averages of four trials. These tests within the same soil 

 did not vary from each other more than three or four minutes except in 

 the peat. 



TABLE 5.— HEAT CONDUCTIVITY OF NATURAL SOILS UNDER LABORATORY 



CONDITIONS. 



The results show that the sandy soil conducts heat most rapidly and 

 is followed respectively by clay, loam, and peat. The difference between 

 the sandy soil and peat is very great, the latter allo^^'ed the heat to travel 

 thru it only one-third as fast as the former. The differences between 

 the other two soils are very small and in favor of the clay. 



HEAT CONDUCTIVITY OF SOILS UNDER FIELD CONDITIONS. 



The heat conductivity of the different types of soil under field condi- 

 tions was determined by taking records every half hour by means of 

 electrical resistance thermometers, which will be explained later, from 



