438 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



feet, has been carried off, aud laid down elsewhere, from a large 

 portion of this State lying east of the Alleghany mountains — aud 

 from the top of these elevations, the entire thickness of the car- 

 boniferous has been removed. The New England States have 

 suffered equally as much. The Western States probably as much, 

 but it is not so easily demonstrable. 



East of the mountains there is another system of denudation, 

 which has effected the upthrows of the disturbed portion of the 

 continent, and widened and deepened, and otherwise modified its 

 valleys. All the mountains have suffered terribly from erosion, 

 none so lofty as to have escaped this action. 



It is as apparent on the White mountains as in the Highlands. 

 I have made some measurements in the Taconic range, and find 

 that from the range lying between New York and Massachusetts, 

 east of the city of Hudson, at least one thousand feet have been 

 shaved off and removed. At this point there are strong signs of 

 glacial action, for the northwest slope of the mountain is grooved 

 and polished, after the manner ascribed to these ice instruments. 



On the summit of the Alleghanies in Maryland, at the crossing 

 of the Baltimore and Ohio railroad, from 700 to 1,000 feet have 

 been removed. 



In a paper read before this Society about one year ago, upon 

 the rocks of this island, I then showed that our gneiss rocks 

 were altered schists, that lie in folded strata, and that from the 

 apex of the folds a thousand feet had been eroded. 



The Highlands have suffered in equal if not greater proportion, 

 and the Shawangunk has not escaped; indeed, it appears as if the 

 whole thickness of the devonian had. disappeared from their 

 summits. 



Bordering these mountains, are some of the most w^onderful val- 

 leys of the continent. The Great Valley has not its equal for 

 definiteness and continuity. It begins in Tennessee and extends 

 under various names through the Atlantic States into Canada, and 

 terminates on the coast of New-Foundland. In our longitude it is 

 known as the Wallkill Valley. 



Its smoothly rounded hills — its gentle slopes, its fertile fields — 

 its well stocked pastures, and its handsome farm houses, are the 

 praise of all who travel through it. To nearly all observers it 

 reminds them of having once been the valley of some noble river, 

 rivalling the Mississippi in volume. Mather supposes our own 

 Hudson to have once flowed through it. Lying west of it is the 



