TEMPERATURE OF THE MOON. 113 



does not reflect as a smooth sphere would do, but very nearly as a flat 

 disk of like reflecting power and filling the same angle. Such a disk, 

 if it diffused all the solar energy which falls on it, would send to us 

 97300 of what the sun does, provided it reflected perfectly in all direc- 

 tions the total incident solar energy. The moon, however, is not such 

 a reflector, and in the visible spectrum the solar light is about 500,000 

 times moonlight. On this scale the curves of the moon given in fig. 90 

 would not be visible. The depression in the lunar curves at 9.6 p. is 



soar 



odine KA! Si 3 O 8 



. Reflections 



(Lang/* 



& 7 & 3 iO 



FIG. 90. Reflection curves of various silicates. 



due to an atmospheric water band. The region from 5 to "j n likewise 

 contains water bands. One can readily see from these curves that a 

 reflecting surface composed of rocks like granite, basalt, diorite, etc., 

 which are mixtures of feldspar, hornblende, and mica, would give a 

 curve similar to that of the moon. 



The general assumption is that the crust of the earth and of the moon 

 have the same constitution, viz, a series of silicates. It follows from 

 the present research that the earth and the moon may be considered 

 8-c 



