DRUMLINS. 281 



shapes, and they would be composed of upper till, not the intensely gla- 

 ciated lower till, unless first eroded and then rebuilt by the glacier. It is 

 difficult to conceive how smoothly rounded hills in such large numbers and 

 of such great size could result from this process. Moreover, some of the 

 masses of thoroughly glaciated matter are long ridges parallel with the 

 glaciation. These are still more difficult of explanation as being due to 

 accumulations in surface hollows of the ice. Osars or sandy ridges would 

 result, not masses of till containing much rock flour. 



3. Are the deep masses of till remains of a former sheet of till of 

 which the greater part has been eroded by the sea waves, as suggested by 

 Prof N. S. ShalerF This can not have been the case in Maine, for the 

 following reasons: 



First. These deep masses of till are sometimes 1 mile or more from 

 any other similar mass. The amount of erosion required is enormous. 



Second. The presence of continuous beaches from high level down to 

 the sea, shown on Monhegan Island and other exposed coasts, proves that 

 if great masses of till had been eroded most of the larger stones would 

 now remain as broad sheets in the valleys or as terraces on the hillsides. 

 On the other hand, the beach gravels of Maine are relatively scanty and 

 bear no relation to the positions of the drumlins. 



Third. The coast region, where the lenticular hills are most numerous, 

 is largely covered by marine sands and clays. If the till was eroded in the 

 manner supposed, the erosion must have occuxTed before the deposition of 

 these marine beds. These beds would preserve the beach gravels beneath 

 them from erosion. No such rolled gravels now exist beneath the clays. 



Fourth. If we suppose that there has been such an erosion of the till, 

 we must account for the fact that the kames and marine deltas deposited in 

 the sea by the glacial rivers have escaped in such good state of preservation. 



Fifth. The lenticular sheets of till on the northern slopes of hills must 

 have substantially the same origin as the drumlins themselves. They lie 

 inclined against the hills and reach upward on the slopes for several 

 hundred feet. The erosion required to carve away the suiTounding por- 

 tions of a former deep sheet of till to such great heights must certainly have 

 left its mark. Yet there are multitudes of these hillside lenses in regions 



'Illustrations of the earth's surface: Glaciers, by Shaler and Davis, p. 63, Boston, James R. 

 Osgood & Co., 1881, 4°. 



