220 OLD VALLEYS. 



That the region around these summit level gorges has been deeply under water, is 

 manifest from the fact already mentioned, that almost always we find accumulations of 

 water-worn materials near each end, sometimes one hundred feet high, as at Willoughby. 

 Other considerations show the water to have been much deeper. The drainage of such an 

 ocean might, in the manner above supposed, have tended to produce the conformation of 

 surface which we now witness, and \vc know of no other mode in which it could be done. 



This hypothesis docs not necessarily require a summit level gorge. It may be applied 

 to the excavation of any continuous valley. Several such valleys exist in Vermont, 

 and the adjacent portions of New Hampshire, whose erosion we can explain in no 

 other way. To some of them we have been able to give so slight attention that perhaps 

 we are unwise to name them. But as we profess to give only hints on this subject, which 

 seems hitherto scarcely to have engaged the attention of geologists, we shall name those 

 valleys which, so far as we can judge, have been produced mainly by the agencies under 

 consideration. 



1. From the mouth of Mulhegan River in Essex county, through Island Pond and Memphremagog. 

 The height of the summit level, at Island Pond, on this route, is 1182 feet above the ocean, but not half 

 as much above Connecticut Kiver, and we can hardly doubt that oceanic and perhaps fluviatile currents 

 once flowed through it. 



2. From Island Pond to the Connecticut River at Barnet, mostly down the valley of the Passumpsic. 

 Of this we know but little. 



3. A valley along the Passumpsic Railroad, from Burke through Barton ; a little beyond which, it en- 

 ters the valley already described from Willoughby Lake to Memphremagog. 



4. A valley passing southerly from Memphremagog, up Black River, through Coventry, Irasburgh, Allmny, 

 Craftsbury and Hardwick, passing to the La Moille, down Alden Brook. A survey of this route superintend- 

 ed by Do Witt Clinton, for a canal, gives the following elevations above Lake Champlain. 



Albany, .... 687 + 90 = 777 above the ocean. 



First Elligo Pond, . . . 710 + 90 = 800 above the ocean. 



Summit Level, . . . 713 + 90 = 803 above the ocean. 



Little Elligo Pond, . . 696 + 90 = 786 above the ocean. 



Sinclair's Rapids, La Moille, 



River in Hardwick, . . 713 -+ 90 = 803 above the ocean. 



Memphromagog, according to Thompson, is 695 feet above the ocean. A rise of 100 feet, it would seem, 

 would throw its waters into the La Moillo. It certainly did onco stand, and for a long time, at an elevation 

 greater than this, as the terraces on its borders prove. All the old valleys above indicated must then have 

 been filled, as must also the whole valley of the Connecticut, and of Champlain, and the Hudson, as well 

 as a multitude of inosculating valleys among the hills. So that at that time the whole country between 

 Connecticut and Hudson Rivers, must have been a lake full of islands, somewhat like Wiunipisiogee in 

 New Hampshire at present. 



5. From Johnson village on the La Moille, to the Missiaco, down Sheldon Creek. We have been 

 credibly informed that a rise of little over 50 feet, in cither of those rivers, would carry its waters into the 

 other. 



6. From Lancaster, in New Hampshire, to the mouth of the lower Amonoosuc. Without much doubt 

 this was an ancient bed of the Connecticut. The summit level is at Whitefield. 



7. Two cases in Huntington. These also have been described in the history of Terraces. 



8. The passage of the Winooski through the Green Mountains. After following this range from the 

 southwestern part of Massachusetts, or even further south, for 140 or 150 miles, :uul limling it unbreaclifil 

 any where, it is truly surprising to see the Winooski cutting a nearly straight course across it to the very base 



