530 



SCIENCE 



[N. S. Vol. XXVin. No. 720 



the Genesee was about five miles south of Por- 

 tageville, where now an immense drift barrier 

 exists. The great apparent width of the Nunda 

 Valley, much wider than the Genesee Valley, 

 which has led almost all observers to accept 

 it as the preglacial continuation of the 

 Genesee, following Hall, is readily under- 

 stood, when it is seen that the valley is worn 

 out on the strike of the strata, and is there- 

 fore of the subsequent or inner lowland type. 

 It lies at the junction of the soft Portage 

 shales and the overlying hard Chemung sand- 

 stones. The latter form a cuesta inface, 

 which rises several hundred feet above the 

 top of the northern boundary of this broad 

 and rather indefinite valley. 



Coming farther south, we find an ancient 

 valley joining the Upper Genesee Valley from 

 the northwest, at Caneadea, where the present 

 river makes a sharp bend. Still farther south, 

 near Angelica, the ancient Black Creek 

 joined the Genesee in a broad valley from the 

 northeast. That the drainage, if southward, 

 continued in the Genesee Valley to Wellsville, 

 and beyond across the Pennsylvania line, and 

 perhaps to the Susquehanna, seems to be indi- 

 cated by the broad character of the Genesee 

 Valley to within a short distance of the state 

 line. The country beyond this point is deeply 

 drift-covered, for we are near the terminal 

 moraine. That this direction was not the one 

 permanently followed by a southward-flowing 

 stream is indicated by the much broader and 

 more open valley which branches off from the 

 Genesee Valley near Belfast, and which is 

 followed by, the Pennsylvania railroad to Cuba 

 and Glean. This valley is as broad, open and 

 deep as is the Genesee Valley. It is a very 

 ancient valley cut into the hard Chemung 

 rocks, and maintains its integrity all the way 

 to the Alleghany at Glean. It is true that 

 south of Cuba the valley is narrower, but this 

 corresponds exactly to the nature of the rock. 

 Near Cuba comes in the heavy Cuba con- 

 glomerate lentil, and a little south of Cuba 

 this forms the bottom of the bank on either 

 side. It is here that the narrowest part of 

 the valley begins, perhaps half a mile to three 

 quarters of a mile at the bottom, though over 

 a mile at the top. This continues until the 



dip carries the conglomerate below the valley 

 bottom, when the valley widens out again. 

 This Cuba outlet forms an excellent one for 

 a southward-flowing Genesee, to the Alleghany 

 and thence to the Ohio, and the Mississippi. 

 On the hypothesis of a northward-flowing 

 stream, a divide must have existed somewhere 

 in this Cuba Valley, unless the Alleghany and 

 perhaps the Ohio also flowed north through 

 the Genesee Valley. Then we are confronted 

 with the remarkable fact that the valley at 

 the divide is as deep and almost as wide and 

 fully as well defined as at any other part. 

 Regarded as the pathway of a southward-flow- 

 ing tributary of the Alleghany, which, gnaw- 

 ing headward, finally tapped the Genesee at 

 Belfast and diverted it into the Alleghany, all 

 its characteristics are readily explained, and 

 it becomes a part of a normal southward drain- 

 age system, of which all the features are 

 normal and perfectly comprehensible. All 

 that is required is a moderate tilting of the 

 land as a whole, an elevation on the north, 

 and a depression towards the south. That 

 there is abundant independent evidence of 

 such tilting is well known, and will be con- 

 sidered again. It will be shown farther on 

 that the relation of these valleys to Lake 

 Ontario is such that only a southward drain- 

 age can explain it. 



Turning now to the Canasaraga Valley and 

 its tributaries, we find that it constitutes an 

 independent system, which in preglacial time 

 had no connection with the Genesee. The val- 

 ley south of Mount Morris, at which point the 

 modern Genesee enters it, is as broad and open 

 as above, in some places even broader, though 

 its sides are steeper owing partly to the harder 

 strata in which they are cut. The preglacial 

 Canaseraga, then, which cut the southern part 

 of the valley, was also fully competent to cut 

 the northern part, without the aid of the 

 Genesee River. As at present constituted 

 the Canaseraga Valley is more than twice as 

 wide as the Upper Genesee Valley, and its 

 rock bottom is more than 600 feet below that 

 of the Genesee. Evidently this was the 

 master stream of the region, whether north- 

 ward or southward flowing. From Mount 

 Morris to Dansville the direction of the valley 



