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of overlying rock which has been worn away, from the close of 

 the Siluric to the present. Where the various members of the 

 Paleozoic form the surface rocks, erosion is correspondingly less, 

 and since the Precambric is at the surface over but a small fraction 

 of the region, the general erosion has been less than that figure. 

 Considering the great length of time involved, this represents no 

 great erosion, and seems to point to land of no great altitude for 

 much of the time. It seems to be further demonstrable that at least 

 one half of this erosion took place in Tertiary time, which argues 

 all the more strongly for general low altitude during the preceding 

 ages of the Mesozoic and later Paleozoic. 



Original drainage 



As uplifted at the close of the Siluric, and following the deposi- 

 tion of the Oswego sandstone, our area became the marginal portion 

 of land masses to the north and the east, and in all probability 

 possessed a gentle slope to the southwest. The original streams 

 must have followed down this slope to the margins of the later 

 Paleozoic water bodies of central New York, # thus flowing in the 

 direction of the rock dip, and at right angles to the strike. Having 

 taken position they would commence to carve valleys, whose possi- 

 ble depth would depend upon the altitude of the land. Streams of 

 this type are called consequent streams. With valley cutting in 

 progress, tributaries to these original streams commence to develop, 

 beginning as gullies in the valley sides, and steadily cutting head- 

 wards. Obviously they form most readily where the valley walls are 

 weakest, and tend to remain in the weak rock belts, following their 

 strike, hence with courses which make substantially, a right angle 

 with those of the original streams. Such streams are called subse- 

 quent, since their development must wait on that of the consequent 

 streams. With a belt of weak rocks to follow, these subsequent 

 streams may eventually become the chief streams of a region, divert- 

 ing or " capturing " the headwaters of the old consequent streams. 

 The Utica and Lorraine shales constitute such a weak rock belt in 

 this region, with the great Ontario valley eaten out along it, the 

 Adirondack highland blocking its extension further east. 



With chiefly low lands, drainage adjustments would go on 

 but slowly, and the drainage may have been considerably modified 

 from time to time by tilting of the land, under these low altitude 

 conditions. With the passage of time, however, it has come about 

 that the chief streams of the region are now in subsequent position. 



