222 VALLEYS EXCAVATED. 



deavored to show, we must admit some of the deepest valleys of the State to have been 

 due to erosion, there is no difficulty in admitting it of all ; but there is a difficulty in ad- 

 mitting it of one or two and excluding it from the rest ; because, if sufficient for one or 

 two it is sufficient for all. 



How far erosion was concerned in forming the Champlain Valley, we cannot say. But we have evidence 

 that it had a share in the work. This is obvious around Whitehall. The rocky ragged hills lying a little 



north of the town, bear decided marks of denudation in their 



Fio. 108. soofca high- outline, as the subjoined sketch (Fig. 108) shows. It was taken 



on the north of Poultney River, just within the limits of Ver- 

 mont, and shows clearly the denudation of the calciferous sand- 

 stone, B, leaving a harder outline, A, of Potsdam sandstone, the 

 river, C, running between the bluffs. 



The junction between the Potsdam sandstone, B, and gneiss, A, (Fig. 109), occurs in the village of 

 Whitehall, which lies in a valley between the two rocks. FIG. 109. 



That erosion has taken place here, and that by fluviatile 

 action, is obvious from the fact that near the junction of 

 the two rocks, probably in the gneiss, pot-holes, D, are 

 found. They are from 6 to 8 feet in diameter, and 60 

 to 70 feet above the lake, as is represented on the subjoined 

 section (Fig. 109), which crosses the valley through the village. C represents the position of the calcif- 

 erous sandrock. 



These facts indicate a large amount of erosion in the Champlain Valley, but will not 

 justify the inference that the whole of it was worn out. We rather incline to the opinion 

 that we may have here some indication of an original depression in the strata, as we 

 probably have in the valley of the St. Lawrence, of which this is the southerly prolonga- 

 tion. But it does not seem to us that we press the facts beyond their natural bearing, 

 when we maintain that probably in all the mountainous parts of the State the valleys 

 are those of erosion. It is an immense and startling conclusion, and until we had care- 

 fully scanned the facts, we shrunk from it, but do not now see how to avoid it. 



DENUDED STRATA. 



But we have other arguments to present on the subject of erosion in Vermont, which 

 go to show that its amount has been far greater than we have yet stated it. The evidence 

 that has been most relied on to prove denudation, is derived from the amount of rock that 

 has disappeared from the tops of anticlinals. It is argued that stratified rocks must 

 once have been continuous, and, where we find large gaps in them, the amount of matter 

 necessary to fill them up is a measure of the erosion. If they have been folded up, as 

 they must be to form an anticlinal, and the top of the fold is gone, we infer that it has 

 been worn away. To take an example in Vermont: The sketch below (Fig. 110) is taken 

 from Section II, and shows the rocks in West Brattleboro, towards Marlboro. There we 

 have on both sides of the anticlinal gneissoid mica schist in the center, next hornblende 

 schist, and beyond this, mica schist. Now the supposition is that those rocks were once 

 united at the top, as represented by the curved lines. And if we could measure the exact 



