518 



STATE BOAkD OF^ AGRICULTURE. 



would liave upon thoir radiating capacity the study jiresented below 

 was undertaken. 



It is unfortunate that natural soils could not also be used for this 

 investigation. The study, therefore, had to be conducted with artificial 

 soils in the followinj; manner: The soil was finely ground, moistened, 

 put into the same vessel as that which contained the core of soil, well 

 compacted, covered with the sheet of mica and the extension box put on. 

 The radiation readings were then taken as in the pnnious case. Then 

 about an inch of the moist soil was removed and replaced by the same 

 kind of soil in a dry and powered form. The box was prepared as usual 

 and the radiation taken again. The difference, if any, between the first 

 and second readings would show whether dry surface with moist subsur- 

 face affected the radiation in any way differently from the moist sur- 

 face and subsurface. The data obtained in this studv are given in the 

 table below : 



TABLi: 16.— RADIATION OF SOILS WITH DRY SURFACE AND MOIST SUBSURFACE. 



This table shows \-ery conclusively that all the different soils with 

 a dry surface radiate less than with a moist surface. In other words 

 a dry surface greatly reduces the amount of radiation. It will be 

 seen that all the mineral soils radiated from 7 to 9% and the peat 15% 

 less when they are covered with a dry thin layer of soil than when 

 all the mass is moist. It is interesting to observe that all the mineral 

 soils radiated about the same when moistened through which confirms 

 the results of the preceding experiment — and that their radiation is 

 cut down to about the same amount l)v their respective dry mulches. 

 The peat, liowever, shows someN\hat a lower radiation. Another note- 

 worthv fact is the insignificant difference in radiation between any of 

 the mineral soils when they are almost saturated and when medium 

 moist. By comparing the first column of the above table with the 

 corresponding one in table 15, it is at once seen that the difference 

 does not amount to more than 1%. In the case of peat, however, the 

 difference runs as high as 11%. 



RADIATION OF SOILS IX DRV STATE. 



^Mention has already been made that the radiating ])owor of the differ- 

 ent types of soil was determined also in their air dry state. This 

 study lias, of course, more theoretical than }>ractical value but it was 

 undertaken with a three-fold purpose in view: It was desired to ascer- 

 tain (1) the relative radiating power of these soils in their dry condi- 



