50 SURFACE GEOLOGY. 



its surface, which tell its origin and mode of deposit. The railroad passes 

 by this route, and the portion in which we are interested is from Sugar 

 river to Claremont junction. East of the railroad Trisback hill rises 850 

 feet above the sea. This obstacle turns back the course of Sugar river at a 

 sharp angle, whence it flows by a long bend on the north side of the hill. 

 The channel of Sugar river is cut 150 feet deep in its original plain, over 

 which its highest floods at the end of glacial time poured into the Con- 

 necticut valley by two routes, one as now north of Trisback hill and Bar- 

 ber's mountain, the other south of these towards Ashley's ferry. The 

 highest portion of this plain in Claremont village is 565 feet above the 

 sea, or 40 feet higher than the river above the upper dam. It thence 

 slopes to 530 feet at one third of a mile east of the junction, and is shown 

 on the east and north sides of the river to West Claremont, sloping to 

 540 feet. The deposits of modified drift which are cut by the railroad at 

 Ellis's bridge, a mile south of Sugar river, and again just north of the 

 junction, being respectively 515 and 500 feet above the sea, are remnants 

 of these plains. They were both brought down at this time by the floods 

 of Sugar river, the former on the north side, the latter on the south side 

 of Trisback hill. The space between these deposits is a swamp, from 30 

 to 40 feet lower, showing that the supply was not sufficient for filling the 

 whole area west of this hill. 



The descent of Sugar river at Claremont village is 125 feet, of which 

 about 100 feet is used for water-power. Below the foot of these falls it 

 descends 100 feet more before it joins the Connecticut at 300 feet above 

 the sea. 



In Charlestown and Springfield the normal high flood-plain of Con- 

 necticut river was probably about 450 feet above the sea, or 150 above 

 the river ; but it is here more obscured by higher tributary deposits and 

 the terracing process of erosion than in any other portion of the valley. 

 It appears to be shown in the broad, uneven terrace west of Calavant 

 hill; probably in that over which the railroad passes south from North 

 Charlestown station ; in the first terrace east and south from Beaver 

 meadow, but not in that of the fair-ground and road northward, which 

 is the delta of Beaver brook ; in the terrace east of the cemetery at the 

 village of Charlestown ; and in the highest terrace, two miles long, above 

 South Charlestown, 



