PREGLACIAL DRAINAGE. 305 



to, as shown in his accompanying map. Thence, according to 

 Newberry, the ancient line of drainage passed through On- 

 tario, and emerged in a stream occupying the valley of the 

 Mohawk, to swell the current of the Hudson rather than 

 that of the St. Lawrence.* 



The facts concerning this line of preglacial drainage had 

 been thus succinctly stated by Professor Newberry in an ear- 

 lier paper : 



Some of the streams draining into the basin of Lake Ontario 

 in former times cut their channels below the present ocean- 

 level. All the salt- wells of Syracuse are sunk in one of these, 

 which is filled with gravel and sand saturated with brine issu- 

 ing from the salina group that forms its walls. The rock-bot- 

 tom of this old river-bed was reached in some of these wells at 

 a depth of fifty feet below the present level of tide- water. 



The valley of the Mohawk is a very deep channel of erosion, 

 now half filled, which must have been traversed by a large 

 stream flowing eastward at a level below that of the present 

 ocean ; and everything indicates that this was the ancient out- 

 let of the basin of the Great Lakes. 



The channel of the Hudson is apparently the only possible 

 continuation of this long line of drainage. As has been re- 

 marked, it is of great and yet unknown depth. The clay by 

 which it is partially filled has been penetrated to a depth of 

 about one hundred feet along its margins. How deep it is in 

 the middle portion can only be conjectured ; but Hell-Grate 

 Channel, which has been kept comparatively free by the force 

 of the tides, is in places known to be nearly two hundred feet 

 deep ; and, since this is a channel of erosion formed by a stream 

 draining into the Hudson, the ancient bed of the Hudson must 

 be still lower, f 



The silting up of these preglacial outlets has enlarged 

 Lakes Ontario and Huron far beyond their previous limits, 

 and wholly created Lake Erie. Lakes Michigan and Superior 



* Paper read before the American Philosophical Society, November 4, 1881, 

 p. 93. 



f "Popular Science Monthly," vol. xiii, p. 16. 



