28 GLACIAL GRAVELS OF MAINE. 



the coast a short distance north of Boston. Such beds must have been 

 foi'med on the coast of Maine as it existed at that pt^'iod. Where are they? 

 That they are now beneath the sea is indicated by the contour of the 

 coast. Prof J. D. Dana has rightly urged that the narrow bays of the coast 

 of Maine correspond to the fiords of Scandinavia and prove that the land 

 formerly stood at a higher level than at present. These bays were once 

 valleys of subaerial erosion, now in part submerged. The obvious conclu- 

 sion is that the only Tertiary beds likely to be found are those which may 

 have been deposited in fresh-water lakes. So far as our present knowledge 

 extends, it must be admitted that no lake or river drift of the geological 

 ages immediately preceding the coming of the ice-sheet has escaped the 

 terrible ordeal of ice. Peats, soils, A^egetable mold, and the bones of land 

 animals must have abounded, but they were either removed entirely beyond 

 the State or were crushed to powder and so incorporated with the rest of 

 the till that no one has been able to recognize them. But negative evidence 

 must not be accepted as conclusive. That such sediments have not been 

 found by no means proves they do not exist and may not yet be discovered. 

 But while sedimentary rocks of the ages immediately preceding the 

 coming of the Ice age have not been found, I have noted many instances 

 of rock weathered in preglacial time. One of the most instructive of these 

 is at one of the slate quarries of Browuville. Most of the rock was planed 

 by the ice to a very level surface. In the midst of the glaciated surface 

 was a depression showing a U-shaped cross section. This was probably a 

 valley transverse to the section, but its true shape could not be determined. 

 The depression was about 6 feet wide and 4 feet deep. The upper and 

 central parts of the depression were filled with the clayey, bluish-gray till 

 characteristic of the slate region, while in the bottom next the rock Avas a 

 rather pale, brownish-red earth, mixed with fractured and Aveathered slate. 

 Some of the nearly A^ertical cleavage laminse of the slate had Aveathered 

 away or fallen to pieces, leaving the more endm-ing laminse. projecting into 

 the reddish earth from 1 to 4 or even 6 inches, thus forming a A^ery rough 

 and serrate surface. This depression was cut across by the quarry excava- 

 tion, and at the depth of a few feet below the depression the slate appeared 

 as solid as the rest of the quarry. Hence there was no reason to suspect 

 the slate of being unusually soft and easily weathered or decomposed by 

 waters beneath the till. Besides, the till Avas compact and unstained by 



