532 



SCIENCE 



[N. S. Vol. XXVIII. No. 720 



Naples quadrangle issued by the state survey. 

 Here we have another series of southward- 

 uniting valleys, easily understood as tribu- 

 tary, with other similar series, through the 

 Wayland Valley, to a southward-flowing Cana- 

 seraga, but difficult to understand if not 

 inexplicable on the hypothesis of preglacial 

 northward drainage. 



If this system drained southward, and there 

 seems to be no escape from such a conclusion, 

 it appears that the Honeoye and Canandaig-ua 

 system originally drained south by way of 

 the Cohocton to the Chemung and the Sus- 

 quehanna, but was diverted by capture to 

 the Canaseraga-Canisteo drainage system. Or 

 it is possible that the Cauandaigua-Honeoye 

 system originally was tributary to the Cana- 

 seraga, and that the Cohocton cut off these 

 more eastern branches from that drainage 

 system, conducting them by a shorter route 

 to the Chemung than is traversed by the more 

 western tributary of the same stream. If 

 that was the case, the capture by the Cohocton 

 was accomplished in comparatively late pre- 

 glacial time, since the Cohocton Valley is 

 Btill narrow, though deep. We do not know 

 enough of the elevations of the rock bottoms 

 of these ancient valleys to decide which is 

 the more likely. 



On the hypothesis of northward drainage, 

 we are again confronted by the anomalous 

 character of the valleys at the point where a 

 divide should have existed. Dryer has pointed 

 out that the broad, open character of the east 

 and west Wayland Valley is incomprehensible 

 on the hypothesis of northward drainage, such 

 a valley being entirely out of place at the 

 divide of two normal river systems which flow 

 in opposite directions. On the hypothesis of 

 southward drainage this valley is easily under- 

 stood. 



It should be noted in this connection that 

 the rock bottom of the Wayland Valley, so 

 far as it is known from outcrops in the beds 

 of streams south of Dansville, is above that of 

 the Canaseraga Valley, the difference being 

 perhaps 200 feet. Since the valley at Dans- 

 ville is a thousand feet deep, not counting any 

 drift-filling in the bottom of this valley, this 

 difference is of no great sig-nificance, so far 



as the importance of the valleys is concerned. 

 It indicates a deepening of the Canaseraga 

 Valley by ice. This is further suggested by 

 the steepness of some parts of the banks of 

 the valley at Dansville, and the local character 

 of the drift which partly fills the southward 

 continuation of the Canaseraga Valley. 



A glance at the geological and topographical 

 maps of the regions around the other Finger 

 lakes shows that they too have the southward 

 drainage expression. Keuka Lake has two 

 southward-uniting branches, the united valleys 

 becoming tributary to the Cohocton. Seneca 

 and Cayuga Lakes are continued southward 

 in more or less open valleys to the Chemung 

 and Susquehanna. That these and many of 

 the other valleys were more or less deepened 

 and widened by ice erosion is, I believe, pretty 

 generally held in spite of objections raised 

 against this idea. The evidence seems to be 

 overwhelmingly in favor of this explanation 

 of their characteristics. 



Let us now consider the evidence which 

 Lake Ontario has to offer in this connection. 

 Opposite the mouth of the modern Genesee, 

 the lake is 576 feet deep. Eighteen miles 

 further east it is 738 feet deep. The surface 

 of the lake is 247 feet above mean sea level. 

 The fall of the Genesee from Mount Morris 

 to Avon is ten feet in a distance of fifteen 

 miles in a straight line but twice that dis- 

 tance by the river. This gives on the average 

 a fall of a third of a foot per mile. The 

 rock-bottom at Mount Morris is 191 feet 

 below the river level; at Cuylerville, four 

 miles to the north, it is 184 feet below that 

 level. At Piffard, four miles farther north, it 

 is 158 feet below the same level. This gives 

 a rise of the rock floor northward, of about 

 six feet for the first four miles and of twenty- 

 six feet for the next four miles. The record 

 at Piffard is probably not of the greatest 

 depth, yet the northward rise of the rock floor 

 of this valley seems to be undoubted. Ta- 

 king the smaller figure, a rise northward of 

 1^ feet per mile, the rock bottom of this an- 

 cient valley at Lake Ontario, forty miles north 

 of Mount Morris, would be 196 feet above the 

 level of Lake Ontario, or 772 feet above its 

 floor (934 feet above its deepest part). This 



