EXPERIMENT STATION BULLETINS. 



517 



of the same size as tlic innor side of the box, until it Avas al)out 1 inch 

 from tlie top of the box. That i)ortion of tlie core which extended be- 

 yond the edge of the other end of the box was cut ofiC carefully with a 

 sharp knife. The box containing tlie core was then placed in a metallic 

 vessel with bottom and no top and made especially to fit this box. That 

 side of the core which rested on the bottom of the vessel, was the sub- 

 soil, while that side which was exposed and came to one inch from the 

 top of the box was the surface soil. The latter side was then covered with 

 a very thin sheet of mica in order to prevent evaporation which would 

 have affected the radiation. This mica being diathermous permitted the 

 passage of the radiant energy. The sheet was of the same dimensions 

 as the box so that it rested upon its edges and was about one inch above 

 the surface soil. Its ends were fastened to the edges of the box by 

 means of paraffin, thus making the box air tight. An extension box 

 .^ inches high and 8 inches in diameter was placed on the top of this 

 other box and was also fastened on by paraflSn. The ends of the mica 

 came then between the edges of the two boxes. The second or extension 

 box was placed there in order to prevent side radiations on the bulb of 

 the thermometer when it was brought one inch from the surface of the 

 mica to receive the radiation of the soil. The metalic vessel contain- 

 ing the prepared soil box was then placed into the constant temperature 

 bath, the temperature of which always remained at about 33° C. and 

 not varying more than 0.2° C. On the top of this vessel were bended 

 horizontal edges by means of which it was hung from the top or cover 

 of the water tank. In this manner the surface of the soil was always 

 below the surface of the water in the tank. The soil was left in the 

 bath about 24 hours in order to acquire the constant temperature and 

 the radiation readings were taken in the same manner as in the preced- 

 ing experiment. The radiating power of the cores of all the different 

 soils was studied, then, in this manner and the results obtained are 

 given in the following table: 



TABLE 15.— RADIATING POWER OF THE CORES OF THE DIFFERENT SOILS. 



It is at once seen that all the different types of soil in their natural 

 and well-moistened condition possess exactly the same radiating power. 

 Water, however, has a different and much higher radiating capacity. 

 Evidently these results agree with those of Ahr's. 



RADIATION OF SOILS WITH MOIST SUBSURFACE AND DRY SURFACE. 



During the warm part of the year the soils have a dry surface and 

 a moist subsurface. In order to ascertain what effect this condition 



