14 NEW YORK STATE MUSEUM 



rock about the west side of the Round lake ice block down to what is 

 now 200 feet altitude. As the total submergence at Round lake was 

 over 375 feet, there had been an uplift of at least 175 feet before the 

 Iromohawk flow entirely ceased. Apparently the subsequent 

 uplift, 200 feet or somewhat less, has not produced much tilting, as 

 the Ballston Lake channel is even now horizontal. All of which is 

 in harmony with the view that the earliest uplift was by a wave of 

 moderate dimensions, 100 miles or less in breadth (18, page 252). 



ROUND LAKE; AN ICE-BLOCK KETTLE 



Three lakes lie in this area which have interesting forms and peculiar 

 relationship to other features. Professor Woodworth regarded the 

 Saratoga and Round Lake basins as " unfilled depressions marking 

 the site of an old valley west of the present Hudson gorge '* (4, page 

 76). Mr J. H. Cook has written on this hypothetical valley (5). 

 The question is pertinent. Why are the depressions unfilled? This 

 is specially pertinent regarding Round lake, as we see that it lies 

 precisely in the path of one of the powerful distributary channels 

 of a great river. Such basins could not persist in the line of heavy 

 drainage loaded with detritus. The sand plains about these lakes 

 are proof of the volume of river-borne detritus. Professor Stoller 

 thought that the Round Lake basin had been filled and was later 

 reexcavated by the stream. He says: *' Deposits of clay and 

 afterward of sand, made widely in Lake Albany, filled in the basin 

 and for the time obliterated it. AVhen Lake Albany began to sub- 

 side powerful currents of water entering from the Ballston channel 

 cut into the deposits. The erosion of the deposits. . . . resulted 

 in the present topography." (7, page 22) His figure (no. 3, page 23) 

 gives four diagrams illustrating this conception of the basin's origin. 

 But it seems impossible for a stream to excavate its own deposits 

 and produce a circular basin of the size and relations shown in he 

 topographic map. It is evident that the basin did not exist when 

 the Maltaville river was flowing. 



The simple and entirely sufficient explanation of Round lake 

 is that it occupies an ice-block kettle. The recognition of drift- 

 buried ice blocks as an agency in the production of basins in moraines 

 and deltas has been the greatest help in the interpretation of these 

 peculiar and formerly inexplicable phenomena. And the explana- 

 tion fits the present case perfectly. 



At full height the sea-level waters lay over the Round lake district 



