GORGE ON DEERFIELD RIVER. 95 



and deposited. Such a rise must have thrown the waters over a basin which ex- 

 tends several miles into Charlemont, as shown on Plate IV. The old river bed 

 is marked on that map, as well as the present course of the stream. It is clear, 

 then, that since the deposition of these terrace materials, the river has not only 

 changed its course a considerable distance to the north, but has cut a new channel 

 80 feet deep, through very hard gneiss rock. It was probably the blocking up of 

 the old river bed by the gravel deposited while the waters stood over the spot, that 

 caused the river to change its course. The evidence on which such an explana- 

 tion rests, is not quite as striking at this spot as at some others of a similar cha- 

 racter to be subsequently described, and, therefore, I will not dwell upon it. But 

 if admitted, it shows us the amount of erosion by the river in very hard rock, since 

 the deposition of the gorge terrace on its banh. And since the terrace lies above the 

 drift, we are sure that so much work at least has been done by the river since the 

 drift period. Nay, after that period, the materials of the terrace at the gorge must 

 have been very slowly accumulated, so that this erosion of 80 feet may not carry 

 us more than half way to the period of the drift. 



At the top of Plate IV, is a section of the mountain through which Deerfield 

 river has cut a passage, as above described : it runs in the direction of the axis 

 of the mountain ; that is, nearly north and south. On the north side of the river 

 the mountain rises to the height of more than 1800 feet above the ocean, and forms 

 Mount Pocomtuck (formerly Walnut Hill). On the south the ridge ascends rather 

 rapidly, till within half a mile it has reached the height of 545 feet above the 

 present river bed. Then it descends 218 feet, into a valley now covered with 

 gravel and boulders, looking like a former river bed. Then the ridge rises for 

 several miles and attains a height nearly equal to Pocomtuck. 



Having ascertained the action of the river 86 feet above its present bed, as 

 proved by the pot-holes, I was led to inquire whether any marks of its erosions 

 existed at a higher level, towards the south. I found that the north slope of the 

 hill exhibited a succession of ragged walls for a considerable height, as shown on 

 the section connected with Plate IV. These have the appearance of successive 

 banks of the river, as it stood at different elevations. These walls present a curve 

 horizontally, whose convex side is towards the northeast, which would be exactly 

 the effect of the river sweeping around towards the southeast in a curve of that 

 description, as it must do to correspond with its present course. (See Map.) 



At first I felt very little doubt that these facts were decisive proof of the former 

 action of this river, at least to the height of 545 feet above its present bed. But 

 some doubts as to this point have been subsequently excited. If the river wore 

 down the whole of this gulf by a slow and uniform action, I can hardly see why 

 the south bank should not have a uniform slope instead of several steps. Nor do I 

 see any reason why it should have changed its bed so many times suddenly, unless 

 we suppose such a state of things to have existed at each lateral movement, as at 

 the last — that is, a filling up of the old bed by loose materials, because the region 

 had subsided beneath the ocean. This would suppose more vertical movements 

 than have generally been admitted. Again, if the sea once, or more- than once, 

 stood over this spot, we should expect that the flux and reflux of the waves 



