222 ROLLIN D. S A LI SB URY A ND ELIO T BLA CKW ELDER 



though no Paleozoic material was found in the deposit. This is 

 the more remarkable since some of the gravels at lower levels 

 in the vicinity contain a large proportion of Paleozoic material. 

 The thickness of this body of drift was not determined, but it 

 probably exceeds lOO feet. The plateau surface between Bald 

 mountain and the known glacial drift has not been studied in 

 sufficient detail to affirm that drift is absent from it, but, if 

 present, it is certainly scattering and meager in the region 

 visited. 



In connection with the problem of the transportation of this 

 detritus, streams and glaciers are the .only agents whose claims 

 need to be considered. Positive evidence in favor of a fluvial 

 origin is absent, so far as known data are concerned, and the 

 existence of numerous bowlders 15 to 25 feet in diameter mili- 

 tates against it, especially as the gradient between the source of 

 the bowlders and their present position is not such as to make 

 their reference to streams seem plausible. The summit of Bald 

 mountain has an elevation of about 7,000 feet, and the (dis- 

 sected) plateau level of the crystalline schists to the west has 

 an elevation of about 8,500 feet some 10 miles. Bald mountain 

 is, indeed, an isolated remnant of this plateau, the surface of 

 which declines eastward from the base of the high part of the 

 range which rises above it. A gradient of 150 feet or less per 

 mile would be altogether inadequate for the transportation of 

 such bowlders as occur on Bald mountain, by any stream which 

 could have had its origin in this range. If river ice be assumed, 

 the difficulty is somewhat relieved, but by no means eliminated. 

 It is to be recognized, however, that the surface gradient may 

 have changed since the deposit was made. 



The general constitution and structure of the material are 

 consistent with its glacial origin, though, except for the great 

 size of some of the bowlders, perhaps not inconsistent with 

 a torrential origin. If the deposit be glacial, the large bowlders 

 present no difficulty, though the absence of Paleozoic material is 

 as difficult of explanation on this hypothesis as on the other. 

 No unequivocal striae were found on the stones of the deposit, 

 though somewhat careful search was made for them. Numerous 



