* ^ Report of the State Geologist. 



which is in full view and close to the station, rises 100 feet 

 higher = 973 ft. This is decidedly above the divide at Horse- 

 heads, near Elmira, and probably nearly corresponds with the 

 highest point that the lake attained, it should be compared 

 with the level of the country at Watkins, given by Fairchild as 

 961 A. T. 



The terraces consist mainly of gravel, with some sand and 

 clay. Amor g the pebbles are many which retain the form and 

 to a slight extent the markings of till-stones, having been trans- 

 ported but a short distance. 



The most acceptable theory of the origin of these delta- 

 terraces is that which refers them to a former higher level of the 

 water of the lakes. The highest deposits of this class attained an 

 elevation which would imply that all of the county north of 

 Ovid was under water (or ice), so that the two lakes may have 

 formed one body of water. 



The period to which this is referred is the close of the Ice Age, 

 while the ice-sheet was melting back from its southern limit, the 

 moraine. At first the water would be confined to the valleys 

 south of Ithaca and Watkins; the outflows occupying independ- 

 ent channels by which they were led to the Susquehanna valley. 

 With the recession of the ice, a point would be reached where the 

 two lakes could communicate with each other; as soon as this 

 occurred, a rush of water from Cayuga to Seneca lake would 

 occur, reducing the level of the former by 140 feet, since the out- 

 let for Seneca lake at Elmira was 900 feet above tide, while that of 

 Cayuga (Fairchild, Gilbert) is 1,010, at Spencer Summit. At this 

 stage Seneca lake would be even higher than when it had only 

 its own drainage to provide for. The mass of water derived 

 from the melting ice was incomparably greater than that now 

 known to us ; suflficient to have converted the lake into a flowing 

 stream three miles wide. 



A third stage began when the recession of the ice front had 

 carried it so far north that an outflow became possible to the 

 eastward into the Mohawk valley. During this stage the lakes 

 appear to have sunk, sometimes by a continuous slow depression, 

 at other times with stages of rest. To the continuous sinking 

 would correspond the lateral ridges of deposit fringing the 

 streams ; to the stages of rest, the terraces with nearly level tops. 



