656 



THE POPULAR SCIENCE MONTHLY. 



An old channel at least 200 feet deep connects Lake Huron and 

 Lake Erie. Detroit is situated on the western side of it, and the rock 

 lies there 130 feet below the surface. 



Many of the streams now flowing into Lake Erie were once tribu- 

 taries to the ancient river which traversed its valley and joined it far 

 below the present water-level. 



The old channel connecting Lake Erie and Lake Ontario apparently 

 passed through Canada between Long Point and Hamilton. Heavy 

 beds of drift, by which it is filled and concealed, here occupy the sur- 

 face. The Niagara now flows over a rock -bed, for this is a compara- 

 tively modern river, which, following the line of lowest surface-levels, 

 passed over a spur from the south shore of the lake-basin when the 

 old channel was filled by glacial drift. 



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 issuing from the Salina group 

 that forms its walls. The rock-bottom 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. 



; '"' Old Mouth 



OF THE 



/ Hudson River 



Fig. 5. Map showing Old Drainage op the Lake Basin. 



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 outlet of the basin of the Great 

 Lakes. 



The channel of the Hudson is apparently the only possible continu- 



