EXPERIMENT STATION BULLETINS. 



647 



lained were in the same order and degree of magnitude as the foregoing. 

 All these results go to show, therefore, that a large amount of heat which 

 is received by the surface of the cultivated soil is radiated back to the 

 atmosphere, which accounts for its small rise of temperature during 

 the day. The objection may be raised, however, that the greater temper- 

 ature on and above the surface of the cultivated over the uncultivated 

 soil, was probably due to the greater amount of evaporation of water 

 in the latter. This is partly correct, and especially when the soils are 

 very moist and the capilary action is very active, but the same results 

 were obtained when the soils had practically the same percent of mois- 

 ture. 



The foregoing explanation concerning the difference in temperature 

 between the cultivated and uncultivated soil is further confirmed by the 

 following experiment. Wooden boxes, 12 inches square and 2 inches 

 high, were filled with moist quartz sand. In one series the sand was well 

 compacted and in another it was cultivated. These two series of sands 

 were then placed outdoors during very hot days and their temperature 

 was recorded every 15 or 30 minutes from morning till evening for two 

 succeeding days. The results obtained are sho-ftTi in the following table : 



TABLE 75— TEMPERATURE BETWEEN CULTIVATED AND UNCULTIVATED SAND— FIRST DAY. 



