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THE POPULAR SCIENCE MONTHLY. 



that the expression, " has been regarded " as a bowlder, has been 

 employed. The reason of this is, that a recent examination of this 

 rock (in March, 1890) has led Prof. Crosby to the somewhat start- 

 ling conclusion that it is not a bowlder, but " simply an angular 

 and prominent remnant of a large granite vein, still undisturbed 

 in its original position upon beds of gneiss ; and that its chief 

 geological interest is found in the fact that, notwithstanding its 



Fig. 5. 



exposed position, it has survived the disintegrating influence of 

 the elements and successfully resisted the pressure of the great 

 ice-sheet." Prof. Crosby also states that, " through the undercut- 

 ting action of the frost, forming quite an extensive rock-shelter " 

 (i. e., the cavity or recess on the lower or valley side), " is afforded 

 an opportunity to observe the actual contact of the massive gran- 

 ite and the finely laminated micaceous gneiss " upon which the 

 granite rests. 



For one of very limited experience to dispute the conclusions 

 of such a trained observer as Prof. Crosby would be presumpt- 

 uous ; and yet it would not seem unreasonable to ask that they 

 should not be considered as entirely determinative without a 

 further careful examination of the problem on the part of ex- 

 perts. The question as to whether the contact of the granite of 

 the assumed bowlder and the underlying gneiss is one of situ- 

 ation or of composition is not an easy one for decision, without a 

 very clear opportunity for examination. The fact that such a 



