96 ON EROSIONS OF THE EARTH'S SURFACE. 



through the depression in the crest of the mountain, which may have existed, 

 would wear it away, as we now find it. After all, however, water flowing in the 

 same direction as the present river, affords a more natural explanation of the 

 erosions at this spot than any other supposition ; and I apprehend that they may 

 have been the result of both kinds of agency: for when a mountainous region, 

 like the one under consideration, is either gradually sinking beneath, or rising 

 above, the ocean, what is at first an ocean, becomes an estuary, and then a river. 



The Ohor 1 is a deep narrow valley, extending from Shelburne Falls to Deer- 

 field Meadows, about eight miles. Throughout most of this distance the stream 

 flows obliquely across the hard strata of mica slate and gneiss, which have a high 

 dip in the same direction as the slope of the stream. The rocks crowd so closely 

 upon the river, and rise so precipitously for several hundred feet, that no attempt 

 has ever been made to make a road parallel to the stream, and only in one place 

 is it crossed by a road, and there with difficulty. Near the upper extremity of 

 this valley we find Shelburne Falls, whose height I know not : but there we see 

 the effect of the cataract upon the hard and almost unstratifiecl gneiss rock, in the 

 formation of pot-holes of enormous size, some of them being as much as twenty 

 feet deep, and eight or ten in diameter. There, too, we see the effect of the 

 expansion of freezing water in the fissures, in the removal of huge blocks from 

 their native beds ; so that upon the whole we cannot doubt that the cataract is 

 receding. Nor can the geologist doubt that it may have receded the whole dis- 

 tance of eight miles from Deerfield Meadows. Nay, perhaps previous cataracts at 

 higher levels, may, in like manner, have worn backwards, so as to form the whole 

 of this Ghor. Its situation is such, and it is so crooked, that it seems difficult to 

 suppose the sea to have had much to do with its excavation, except, perhaps, to 

 widen its upper part. 



b. Ancient River Bed at the Summit Level of the Northern Railroad in New 



Hampshire. 



On Map No. 1, a mountain ridge is represented as running from Connecticut 

 river, at Bellows Falls, northeasterly to the White Mountains. No such distinct 

 mountain exists there : but it marks the dividing ridge between Connecticut and 

 Merrimack rivers. The valley of the latter is about 150 feet lower than that of 

 the former. Through this dividing ridge I know of not more than four depres- 

 sions of considerable depth. One of them is in the town of Orange," on the 

 Northern Railroad, and is 682 feet above the Connecticut, at Lebanon, and 830 

 feet above the Merrimack. Another is at Whitfield, on the White Mountain Rail- 



1 The Geological Class in Amherst College, a few years ago, having forced their way on foot 

 through this wild and difficult gully, seldom trodden by man, felt at liberty to propose for it the 

 Arabic name of Ghor; which may be used till a better one is suggested. In like manner, the class 

 that graduated in 1856, visited Walnut Hill, referred to in the test, and imposed upon it by ceremo- 

 nies, the name of Mount Pocomtuck ; the Indian name for Deerfield river, which washes its southern 

 base. 



