288 GLACIAL GRAVELS OF MAINE. 



4. The glaciatiou of the country south of the Waldoboro moraine 

 differs in no respect that I can discover from that of the country north of 

 it, and the same is true of Portland. There is no sign of the subaerial 

 erosion that would result if the ice only advanced to these places after a 

 retreat at all comparable in time to the interg-lacial epoch of the West, sup- 

 posing the land to have been above the sea. On the other hand, if it was 

 beneath the sea during all or even a part of the interglacial^ period, we 

 ought to find a different development of the marine beds south of those 

 places (the supposed line of ice front during the second advance of the ice) 

 from that north of this line. I do not recognize any difference except the 

 general change we discover everywhere as we go to greater ' elevations up 

 to 230 feet. 



5. If the suj)posed readvance of the ice at Portland over marine beds 

 is correlative to the second glacial advance over the Northwest, we ought 

 to find everywhere along the coast a series of terminal moraines or morainal 

 sheets overlying the marine beds. Only a few places have been found 

 where tlais can be admitted as even remotely probable. The few scattered 

 bowlders in the marine clays can better be accounted for as due to ice floes 

 and small bergs. 



6. Existing glaciers are known to advance and retreat alternately, or 

 for a time remain stationary. Analogy requires us to jjostulate similar 

 behavior of the great ice-sheet. It is not necessary to correlate the time of 

 such temporary halts of the extremity of the ice, or of its readvances, with 

 the interglacial period of the Northwest. They may have been only for a 

 few years at most; not a geological epoch. The small terminal moraines 

 and supposed readvances of the ice in Maine correspond generically to the 

 smaller retreatal moraines of southern New England and the Northwest. 

 At the time of their formation the doom of the last ice-sheet had been pro- 

 nounced. The algebraic sum of the secular accumulation and waste of ice 

 had the minus sign, though particular elements might be plus. 



7. It is granted that a. thin body of ice might advance over marine 

 sediments without eroding them, just as happened with the soils of the 

 Upper Mississippi Valley. But if the flow were to continue long enough to 

 equal the second advance of ice over the Northwest, a considerable body 

 of till, both subglacial and englacial, ought to be left overlying the clays. 

 The finding of only small masses of till or a thin sheet of scattered bowl- 



