40 SURFACE GEOLOGY. 



above the sea, or 190 feet above the river at the foot of the falls. The 

 middle terrace here rises in going south from 435 to 455 feet; and its 

 material, well shown by a long railroad cut a sixth of a mile west of the 

 upper falls, is mainly fine and coarse gravel, quite in contrast with the more 

 common sand and clay. This difference in material is clearly explained, 

 however, by a gap in the kame, which has been cut through and swept 

 away by the river above the falls and on the north-west side of this ter- 

 race, which has been formed from it. Tributary streams have also often 

 brought down coarse gravel deposits, forming deltas or contributing to 

 the normal high terrace-plain, which on this account is often difficult to 

 be precisely distinguished. Mascomy river, in Lebanon, and Little 

 Sugar river, at North Charlestown, especially, have brought in these 

 coarse deposits in large amount, changing the character of all the modi- 

 fied drift to a mile below their mouths. 



A quarter of a mile south-west from White River Junction we find an 

 ancient bed of White river, similar in position and height, and formed 

 and deserted under the same causes with that of Pompanoosuc river (p. 

 37). This is a nearly level depression, 300 to 400 feet wide, 25 feet be- 

 low the alluvial plain on the west, and 60 feet below the gravel ridge or 

 kame on the east. Its height is 154 feet above the river on the north, or 

 487 feet above the sea. It descends only three feet in going 1,000 feet 

 to the south, where the high plain in which it was formed, and the ridge 

 which was its eastern barrier, have both been washed away. 



Through Hartford and Hartland the upper terrace is well exhibited, of 

 a normal height 525 to 500 feet above the sea, or nearly 200 feet above 



Hartland d 



o Delta Lull's o d o depot. Kame. d ^ d d 



sea. 



Ficr. 10.— Section in Hartland and Plainfield. Length, i^ miles. 



the river, and reaching one third to one mile back from it ; but in several 

 places this is broken by hills of ledge or till, isolated or extending across 

 it nearly to the river. Its normal height is increased 40 to 80 feet by 



