320 GLACIAL GEAVELS OF MAINE. 



the map of all the streams of the ice-sheet, enoug-h is known to enable us 

 to mark ont the courses of the larg-er rivers. In some cases the gravel is 

 residual rather than transported — that is, the streams had barely power to 

 cany off the finer matter of the till, leaving- the larger fragments with but 

 little, if any, water transportation from the place where the ice brought 

 them. In a multitude of cases no doubt small trickles and brooklets car- 

 ried off some of the finer matter of the till, leaving it a little more sandy 

 than the usual till, but such we can hardly trace. In a number of places 

 glacial streams formed potholes, but have left no gravels. In places 

 we find the groimd moraine eroded and glacial gravel left at some point 

 southward. 



Although the general or average directions of the rivers were roughly 

 parallel to the direction of ice floAv, there are maiiy important divergences. 

 Most of the shorter meanderings are plainly transverse to the scratches on 

 the rocks, and so are some of the larger zigzags of 5 to 30 miles. The maps 

 show that a number of the osar rivers had tributary branches like those of 

 ordinary rivers, and at their places of junction I haA^e found no proof from 

 the scratches that there was a similar convergence of the ice movements. 

 In like manner, where the delta branches diverge, there is no corresponding 

 divergence of the scratches. Thev diverge or converge at large angles up 

 to a right angle, and it is difficult to conceive causes for such ice move- 

 ments. It is true that the latest ice movements were recorded by shallow 

 scratches on rocks bare of ground moraine, and from which the glaciated 

 surface has now generally weathered, aided by forest fires or by those made 

 in clearing the land. But after making the largest admissible allowance 

 for the imperfections of the record it is still difficult to assign causes for 

 such a converging flow as must have taken place near the head of Penobscot 

 Bay (the reader is referred to the map, PI. XXXI, for explanation), or in 

 Greenbush, or near Tomali station of the Maine Central Railroad.. As 

 elsewhere noted, there is a convergence of glacial rivers toward Columbia 

 and Jonesport. The scratches also converge toward the same region, but 

 not so much as the rivers. The Coast Survey charts give the soundings for 

 a few miles off the coast, and I fail to find any deep valley in the sea floor, 

 or other topographical reason for such a converging flow of the ice; and 

 there is just as little topographical reason for the flow of the rivers for 30 

 miles or more transversely to the ice movement, as testified both by 



