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SMITHSONIAN MLSCHLLANEOUS COLLECTIONS 



[vol. 47 



ing approximately the magnetic variation. The natural inference is 

 that the phenomenon is due to the reflection of heat from the upper 

 surface of the boulder, this action being at a maximum when the sun 

 is upon the meridian and reaching much farther out on the northern 

 side than upon the southern, where the rays would strike but a short 

 distance from the base of the rock. A tin reflector, such as is used 

 for cooking, was found to give the same effect when left for a few 

 days upon the snow. This explanation, however, was found to be 

 unsatisfactory in certain cases where the upper surface of the 

 boulder was inclined in the wrong direction to deflect the heat to the 

 north, and so left the entire matter in doubt. 



I'n.. 77. Melted area on the north side of a surface block, Victoria glacier. 



[2. Ice Temperatures. — A few observations were taken upon die 

 temperature of die ice near the front, in the abandoned tunnel to which 

 reference- lias be< n previously made. A hole was bored witb an auger 

 into the face of the ice. back 140 ft. from the entrance, and a standard 

 minimum thermometer inserted. This was estimated to be 70 ft. 

 back from the ice- foot and about 17 ft. from the actual ice face. 

 1 >uring the week July 31 to August 7. the readings were 31.8 , 3 1 .6°, 

 31.8 . 31.9 . 31.7' and 3_' I-'., the maximum temperature of the air 

 in the tunnel ranging from 31.4 to 33 F. Owing to the effect of 



