CLEVELAND MORAINE. 649 



half that of the morainic filUng. The pits are iu some cases fully 20 feet in 

 depth, though usually much less. Excavations in and near Falconer show 

 the material to be largely gravel and fine sand, there being but little coarse 

 gravel and cobble. 



This gravel plain has a continuation up Gonewango Creek Valley 

 above the junction with the Chautauqua outlet, occupying the valley as far 

 up as Kennedy. It stands about 60 feet above Conewango Creek and 

 carries numerous basins. The basins are usually shallow, 3 to 5 feet in 

 depth, but occasionally reach 10 feet. This pitted gravel plain seems to 

 have been formed by waters from Cassadaga Creek as well as from 

 Conewango Creek, for it fits about the southern end of the low plain in 

 Cassadaga Valley. As indicated above, neither Cassadaga Creek nor 

 Conewango Creek has a well-defined moraine at the head of the gravel 

 plain, such as appears in the Lake Chautauqua outlet at Jamestown. 



The lines of outwash farther east, on a tributary of Great Valley 

 Creek near Plato, on Big Meadow, on Ischua Creek near Machias, and at 

 Eagle have already been discussed. The strongest of these are on Big 

 Meadow and on Ischua Creek, each being fully a half mile in width; 

 the others were apparently weak lines of discharge. 



In the Genesee Valley a lake was formed, which, as indicated on 

 p. 201 et seq., had its discharge to the Allegheny River past Cuba, N. Y. 



A word of explanation seems necessaiy in support of the opinion, 

 already several times expressed, that the lakes along the outer margin of 

 the moraine occupy basins which owe their origin to the ice sheet. These 

 lakes have considei'able depth (portions of Conneaut Lake being 100 feet 

 deep), yet they are so situated in reference to the moraine, being in an 

 open valley on its outer border, that they should have been filled with an 

 outwash from the ice sheet, unless some obstacle not now present opposed 

 this filling. No other obstacle is known but ice. It therefore seems proba- 

 ble that these lakes, and others of similar position, owe their existence to 

 the presence of large masses of ice in the vicinity of or just below the ice 

 margin. The smaller basins of pitted outwash aprons and moraine-headed 

 terraces are also supposed to owe their existence to the presence of large 

 masses of ice in the flooded outer border tract. In most cases there was 

 probably no transportation and grounding, but simply a persistence of the 

 ice there after it had melted away from adjacent parts of the valley. 



