354 R. S. TARR — LAKE CAYUGA A ROCK BASIN. 



less accentuated toward the north and the tributaries entering througli 

 shallower valleys, the assumption is warranted that this is the direction 

 of flow. In lake Cayuga valley, as is stated in the first section of this 

 paper, this is the case in the northern end. This argument of itself seems 

 to me conclusive, and the others are introduced merely as confirmation. 



But, if more proof is needed, we ma}^ point to the pregiacial tributaries 

 of Cayuga river. Six Mile creek, about a mile and a half from the head 

 of the lake, had its pregiacial channel about 50 feet above the present 

 lake surface; Salmon creek, seven or eight miles farther northward, 

 flowed at an elevation of about 20 feet above the present lake-level, and 

 the valley near Aurora had its level slightly below the level of the lake. 

 There is, therefore, as indicated by the tributaries, a constant river slope 

 toward the north. 



Evidence that 'Lake Ontario is a, Rock Basin. — It seems to me that we 

 may fairly conclude that the direction of flow of Cayuga river was north- 

 ward. It was, then, in all probability, tributary in some way to the 

 stream which passed through the valley of the present Lake Ontario, 

 which is but 40 miles distant ; but at present the surface of this lake is 



BT^ried 

 VaUcy 



FiftURK 2. — Pregiacial Valley, Cayuga Lake. 



Exaggerated vertically to show the northward slope of the pregiacial Cayuga river as indicated 

 by the tributaries. 



246 feet above sealevel and the bottom 738 feet below the surface, or 492 

 feet below sealevel. Is it possible that Cayuga river, a mature stream with 

 a gentle slope for a distance of 40 miles, should, near its mouth, so in- 

 crease its slope as to fall about 800 feet in the distance of 40 or 50 miles ? 

 Is it not, rather, that Cayuga river flowed with the normal slope and 

 entered a river whose channel was not below the present surface of lake 

 Ontario, but, on the contrary, above it? 



Here the inquiry naturally arises as to whether the foregoing facts do 

 not indicate that lake Ontario is also a rock basin ? 



It may seem that this is not a warranted conclusion and, indeed, it is 

 put forward only tentatively, as a suggestion, in the hope that it may 

 stimulate some one to look for evidence of the same nature as that used 

 in the discussion of the origin of Cayuga. There may, it is true, be a com- 

 plication of rock-folding which shall make the problem of the origin of 

 lake Ontario less simple. 



The evidence seems to the author to be very suggestive. A series of 

 valleys extend toward lake Ontario and reach a point only forty or fifty 

 miles distant, the intervening area being a drift-covered plain. Cayuga 



