Tlie Parallel Drift-BilU of Western New York. 257 



eight inches of blue clay, the till was reached ; and the first 

 shovelful of earth, coming from below the blue clay, contained 

 a small sub-angular boulder of blue limestone, covered with, 

 striae almost as fresh as if made yesterday. Less than half a 

 mile down this same valley, which is cup-shaped, and even now 

 supports a growth of tamarack, the muck and peat were sounded 

 with a pole to the depth of fifteen feet without finding solid bot- 

 tom, and a quarter of a mile further south, in a cutting made 

 to drain the swamp, the boulder clay was seen. 



Instances might be multiplied of sections observed in ditches 

 through uplands and lowlands, in cuttings for roads, etc., all 

 showing the till in the same general character, however different 

 may be the surface deposits. 



We have here, then, two different kinds of drift deposits, the 

 superficial and the deep. It remains to consider how they were 

 placed in their j^resent positions. 



When the geological survey of New York wns made, more than 

 forty years ago, the jseculiar arrangement of the drift in this re- 

 gion was noted, and the opinion was expressed that the materials 

 were deposited by streams of running water (Eeport of the 4th 

 Dist., Hall). Since that time, other writers have expressed a like 

 opinion with various modifications. Some have supposed that 

 a broad sheet of glacial drift has suffered aqueous erosion; in 

 other words, that the valleys have been cut by streams, and that 

 the steep northern declivities of the hills are proof that the 

 streams fl.owed toward the south. 



That the first explanation is insufficient, in the present state 

 of geological science, is evident at a glance. Eunning waters 

 do not deposit unmodified boulder clay, such as we have shown 

 this to be. 



Examination Avill show the second explanation quite as unsat- 

 isfactory. The first objection is that the valleys are cup-shaped 

 depressions in the drift; ihe second, that there is an entire ab- 

 sence of such accumulations of river gravel as must have remain- 

 ed had a broad sheet of glacial drift been cut by streams. 

 Either of these objections is fatal to the theory. 



From the evidence which I have presented, I think but one 

 conclusion can be reached, namely that the drift was deposited 

 here in nearly its present form by a glacier, at least, all its deeper 



