THE GLACIER THEORY. 105 



Yon observe, further, that these bowlders have been nicely 

 polished upon their surfaces, and the edges so ground down 

 and rounded, that they resemble the stones we find upon sea- 

 beaches which have been under the action of the waves for 

 long periods of time. All these facts and appearances point 

 to the action of water, or, more distinctly, to the action of 

 ice and water. Now, as I find these rocks upon a hill one 

 hundred and twenty-five feet high, or that height above the 

 surface of Lake Kenoza, the question arises. How could water 

 and ice reach that point to exert such extensive influences 

 upon the hard surAices of rocks? This inquiry leads to a 

 brief consideration of a period in the history of our planet 

 known as the great Ice Age, which is supposed to have existed 

 during a portion of the post-tertiary period. 



Assuming that the bowlder rocks upon my farm, and upon 

 your farms, gentlemen, haye been brought by the agency of 

 ice to their present positions, let us inquire as to the area 

 over which this movement extended. 



If we look over the map of the United States, and survey 

 all that immense extent of country north of the line of 40°, 

 we obtain some idea of the magnitude of this movement, so 

 far as North America is concerned. The area covered by 

 drift includes the whole of New England, New York, Penn- 

 sylvania, Ohio, and some of the Western States. All over 

 this section we find these bowlder rocks, and in association, 

 we find immense deposits of gravel, slate, sand and clay, 

 all mingled in a homogeneous mixture, with the exception of 

 the blue clay, which usually forms a distinct layer. A theory 

 formerly prevailed, and is even now entertained by some 

 geologists, that this portion of our country has been sub- 

 merged ; that the sea, or salt water, covered the whole of 

 this vast area in a comparatively recent geological period ; 

 and that floating icebergs, coming from the north, were 

 the carriers of these stones, gravel, etc. It is undoubtedly 

 true that icebergs are capable of transporting stones, and do 

 transport them long distances in our own period, but this the- 

 ory does not account for all the observed facts. There are 

 certainly a great number of difficulties in the way of the 

 adoption of this hypothesis. In the first place, there is not 

 evidence sufficient to prove that the New England States, or 



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