DISCUSSION AND INTERPRETATION 459 



Canandaigua streams were southward flowing, consequent tributaries of 

 the Genesee, and the Honeoye and Bristol streams were obsequent trib- 

 utaries of a subsequent stream which occupied the Rush-Victor drainage 

 channel. The southward convergence of the Canandaigua and Cana- 

 seraga valleys and the relations of West River valley to Canandaigua 

 and of Conesus to Canaseraga are in consonance with this hypothesis, 

 and do of themselves suggest that the drainage of the region was orig- 

 inally southward. This, of course, demands a glacial filling in the 

 Cohocton-Wayland valley of more than 600 feet. A few deep borings 

 in that valley would set this questionat rest. 



4. During the maximum extension of the Labrador ice-sheet this part 

 of the Finger Lake region was 60 miles back of the glacial front, and was 

 probably buried under several thousand feet of ice. During the late 

 Wisconsin period of glaciation the ice-sheet became strongly digitate, 

 and each north- south valley was occupied by an independent lobe, which 

 endured long enough to build a terminal moraine of imposing mass, and 

 in some cases valley-side moraines of smaller but notable bulk. The 

 drainage from these ice-lobes deposited extensive outwash plains on the 

 distal side of the terminal moraines. The conspicuously drumlin-shaped 

 ridges and the U-shaped, oversteepened valleys are precisely such as 

 characterize an ice-molded topography. Marrowback hill, Bald hill, and 

 the basins of Hemlock and Canadice lakes might be taken as typical 

 examples of the effects of glacial erosion on stream valleys and inter- 

 stream ridges previously carved in soft and friable rocks. 



The relation of Canadice valley to Hemlock as a hanging valley at 

 both ends adds emphasis to the general expression of glacial sculpture. 

 As the work of stream erosion alone, Canadice valley seems inexplicable. 

 Whether it is assumed to have been originally the valley of a single 

 tributary of Hemlock or to have been produced by the headwater erosion 

 of two streams flowing from a midway divide, the small watershed and 

 short course of such streams would have rendered them incompetent to 

 erode a valley of anything like the present dimensions. The h}^pothesis 

 that both Hemlock and Canadice valleys have been deepened and 

 widened by ice erosion, but that Hemlock, lying directly in the line of 

 ice-motion, was more profoundly modified, while Canadice was occupied 

 only by a diverticulum of the glacial stream, would fairly account for 

 their present forms and relations. In that case their present discordance 

 of level, amounting to at least 250 feet, would furnish an approximate 

 measure of the differential deepening suffered by the two during the 

 glacial epoch. 



All the evidence thus far discovered in the region under discussion 

 points to the conclusion that the peculiar features by which these val- 



