EROSION SOUTH OF ST. LAWREXCE-MISSISSIPPT WATERSHED '28o 



"Now, this is merely a torrent earrylng clean stones. If we have these 

 stones mingled with ice (not frozen to them) the carrying power of the ice 

 aids the current, as the torrential power of the water drives ice and stones 

 together wherever the current reaches to the hottom of the trough. 



"If we in addition consider the ice actually frozen to the stones we shall 

 see that there is nothing to prevent the statement that gravels of any size may 

 he transiK)rted in a glacial overwash. 



"2°. A second deposit due to ice, which would also be stratified, would occur 

 when the current, which is always more sinuous than the channel, would 

 strike against a gentle slope and force the large cakes with their high momen- 

 tum sliding up the slope. This is the case of sporadic gravel patches along 

 the Juniata, which are over 100 feet above present water level, while the 

 average of the gravels is but 80 feet -above that level. 



"3°. Wherever a sudden widening of the vallej" formed a cove, across which 

 the current did not flow, an eddy would form, and into the cove would drive 

 the bergs, circling in a path influenced by the contours of the sides and drop- 

 ping their burden from the grinding action of the mass rather than its abla- 

 tion. This would not be usual iceberg clay formed in still water, but a more 

 or less stratified mass. A very good example is Fountain Hill, a part of South 

 Bethlehem, I'ennsylvania, which is an eddy hill formed of gravels and huge 

 masses of rock. One Medina mass was 11 feet long, 5 wide, and 3 thick. 

 These huge stones were in the core of the hill, and around them were stratified 

 gravel, rising over 100 feet above the present level of the Lehigh. 





FiOTRE 1. — DUif/ratn iUiistrathifj the Effect of torrential Affliirvts on the main Stream 



No. 1 is the state of affairs before the trouble begins. A-B is a torrential side affluent 

 into C-D, a stream with lower velocity, and with the checking of the current of A-B 

 there forms a sedimentary deposit which forms a ridge in the bed of the main stream. 



"One thing noticeable in the Warren [Pennsylvania] gravels was the infre- 

 quent, but constant presence of large cobbles in strata of finer gravels and 

 sands, and in a small lenticular stratum of fine quicksand was found a mass 

 of native copper, or rather a nugget, about 5 inches long and a little thicker 

 than the thumb. Considering the difference in size, and still greater difference 

 in specific gravity. I felt that only floating ice could thus mix things. 



"4°. The accumulations of debris dropped by the ice driven up the hillsides 

 by momentum or sporadic dams would be. under the. influence of a changeable 

 current, diverted by lodgments of ice that did not readily dislodge, so that 

 such a current deflected transversely to the general direction would sweep 

 away these sporadic accumulations into still water and form a pile out of the 

 general direction of sedimentation. 



"5°. Then comes the usual case of a deposit in the form of a bar wherever 

 the current swept round a hill ; but such a deposit would run up the hill and 

 not be isolated from it, as would be the case with the 'eddy' bills above noted. 



"C°. Wherever a side attiuent came in at a wide angle, there would be a ten- 

 dency to form an eddy. The general case here' is like a long eddy hill. 



XX— Bull. Geol. Soc. Am., Vol. 23, 1911 



