Of 

 Ul 



> 

 O 



*£ 

 I/. 2 



; £<7 



%/> Hi 



m '■'21IA 



z z ,- 



^ - W- 



PERCENTAGE 



Figure 59. The passage of radiant energy 

 through a snow cover. 



actually entered into the snow cover, and not the total energy which had fallen on its surface and 

 had been partially reflected. 



In summing up the results of his investigation of the radiational properties of natural fresh 

 ice, Kalitin arrives at the following conclusions: 



1. Ice is easily penetrated by radiant energy within the limits of wave lengths of 0. 35 to 

 3. microns, i. e. , by the shortwave part of the spectrum. 



2. As can be seen from figure 60, ice is more transparent to scattered radiation than to 

 direct (radiation) . 



^0 SO BO 10 iO 30 

 PERCENT TRANSMITTED 



Figure 60. The change of ice trans- 

 parency for direct (smooth 

 curve) and scattered (dashed 

 curve) solar radiation as a 

 function of ice thickness. 



3. The transparency of ice is very much affected by the air bubbles imbedded in it, 

 whereupon porosity being equal, small bubbles, due to which there is a great deal of scattering of 

 the incident radiant energy, makes the ice less transparent than large bubbles. 



It is noteworthy that ice which to the eyes appears to be completely homogeneous, very trans- 

 parent, and which contains no visible air bubbles, may prove to be more transparent to scattered 

 radiation. 



176 



