1-iJ- G. H. Stone — Glacial Sediments of Maine. 



thus retarding the melting. The net result of all the forces 

 involved was that the waters were diverted into the valleys 

 during the last days of the ice-sheet. The ice in contact with 

 the water melted more rapidly than the ice of the uplands 

 which was readily drained. The time came when the streams 

 extended across the whole of the lower part of the valleys 

 while much ice still remained on the hillsides. We might call 

 the vast streams, which then tilled the valleys, ordinary rivers, 

 since they were not bordered immediately by ice. Yet the 

 seepage of ooze and flow of Gletschermilch, silt and sand, 

 which had helped till the broad channels of the osar-plains 

 period, still continued from the uplands with even greater 

 rapidity. At the place of deposition over the bottoms of the 

 valleys this drift was fluviatile, but with respect to the ice that 

 still remained on the uplands it was frontal matter. 



In large part the valley drift is a frontal plain of glacial 

 sediment. In several of the north and south valleys the cen- 

 tral part of the plain of so-called valley drift is an osar-plain 

 proper. Given a broad channel and a more rapid melting of 

 the ice at the sides of the channel as we go southward, it is 

 evident that at some point the stream will have broadened so 

 as to extend across the whole bottom of the valley. All the 

 sediment below this point will be a frontal plain with respect, 

 both to the osar-plain river flowing from the north and also 

 with respect to the multitude of small streams and seeps from 

 the ice on the hills at the sides of the valley. As the enlarge- 

 ment of the glacial channel proceeds northward, the frontal 

 plain is extended at the same rate. We thus have sediments 

 that were deposited along the axis of the valley between ice 

 walls ultimately flanked and more or less covered by frontal 

 matter. It will usually be very difficult to distinguish the osar- 

 plain from the frontal plain, since they blend one into the 

 other by degrees. 



The writer has not explored the upper portion of the valley 

 of the Connecticut River and therefore cannot venture a 

 positive opinion. But the descriptions of the alluvium of this 

 valley given by Messrs. Hitchcock, Upham and Dana are not 

 only consistent with there having been an enlarging ice-channel 

 along the axis of the valley, but are highly suggestive of that 

 hypothesis. The alluvial drift of the lower course of the 

 Aroostook River and the middle course of the St. John has 

 very nearly the same character, with perhaps a larger admix- 

 ture of frontal matter. 



The osar-plains also help us solve the question, long mooted, 

 of the origin of the river terraces. 



It will be noted that the above outlined conception of the 

 Yalley Drift epoch, though derived from a strict induction 

 from the facts as observed in Maine, is in many respects not 

 very different from that of Dana's Manual. 



