tn the Champlain and Terrace Periods. 468 
- ae the descendin fone increasing in depth in the 
same way that additions are now made to the phage pas or 
intervals, of our large rivers by the annual floods o i 
The terraces began to be formed as soon as the ae of 
material became insufficient to fill the place of that excavated 
y the river. We must suppose that this process of erosion 
was slow, allowing the river to continue for a ong ti me at 
nearly the same level, undermining and wearing away its bank 
on one side, and depositing the material on the opposite side, 
till a wide and nearly level lower flood-plain would be formed, 
bordered on both sides by steep terraces. When the current 
arrived at or confirmed oe long study of these deposits 
this valley and throughout New Hampshire. 
The sources of Connecticut river are a series of four lakes, 
the highest of which, covering only a few acres, is 2,550 feet 
above the sea. The lowest of the series is Connecticut Lake, 
three square miles in area, 1,618 feet above the sea. Heights 
of the river, with distances {rom Connecticut Lake, are as fol- 
lows: Mouth ‘of Hall’s stream, 15 miles, 1,085 feet ‘above sea, ; 
at Colebrook, 24 miles, 1,010; at North 'Stratford, 37 miles, 
891; at Groveton, 49 miles, 854; at Lancaster, 56 miles, 835 ; 
mouth of John’s river, 68 miles, 330; at Upper Waterford, 74 
remind of Minnesota, who held this yer! as early as 1872. See Proc. Amer. 
nce, vol. xxi, 1872, p. 165; Geologygof Minnesota, First 
b> 
ni 
ralcg the glacial period, wile} insufficient to discharge these incre 
floods, and would become obstructed ‘the detritus which they brought. 
