rl34 NEW YORK STATE MUSEUM 



To one not familiar wltli glacial phenomena the above explana- 

 tion may seem imaginary and farfetched, but it is undoubtedly 

 the true one. Such depression®, either dry or containing lakes, 

 are not rare in the upper stretches of valley plains that have been 

 occupied by glaciers. In the district of our present study the 

 reader can see by the maps that several of the valleys leading 

 south from the divide have small lakes, but only near their heads. 

 Such lakes, in order from east to west, are East Mud lake, Mud 

 lake, Cassadaga lakes and Bear lake. Probably many small lakes 

 and lakelets which once existed have been obliterated by 

 vegetal growth or other filling. 



The more common occurrence of detached ice-blocks imme- 

 diately south of the divides was due to the loss of motion in the 

 edge of the ice sheet which overhung or projected beyond the 

 crest of the divide. In other words, as the direction of ice move- 

 ment was changed on the angle of the divide from a down-slope 

 to an up-slope, the portion of the glacier on the down-slope was 

 left stagnant, and at the mercy of the stream action. 



The other inconsistency, the absence of waterways across the 

 divide, is not so readily explained. The fact of a flow of water 

 across the divide must be assumed, whatever the exiDlanation of 

 the phenomena. We need not mention all the suggestions which 

 might be made, but which a little thought or investigation would 

 show improbable or impossible. For some cases the explanation, 

 may possibly be that the divide has been shifted to the north 

 since glacial time. That by the northward differential uplifting 

 some point which in glacial time was lake bottom, and north of 

 the divide, has been lifted so as to become the present divide, 

 and that the water parting of glacial time was at some point 

 which is now down stream and under alluvium in the south-lead- 

 ing valley. The Dunkirk sheet will show the reader that from 

 the upper Cassadaga lake down the valley 7 miles there is a fall 

 of only 6 feet, according to the map. The deformation of the 

 region, as shown by the ancient beaches in the Erie basin, is 

 between 1 and 2 feet to the mile. This is more than the amount 

 of fall in the Cassadaga valley -at the present time. But this 



