No. 6.] UPHAM — GEOLOGY OP NEW HAMPSHIRE. 335 



chusetts, the terraces are very numerous, frequently four or five 

 on a side, and reaching a height of 100 to 200 feet above the 

 stream. In the upper Connecticut valley and along Merrimack 

 river, the alluvium principally consists of the bottom-land or 

 interval, and the high terrace or plain, which averages about 

 100 feet above the river. Both the terraces and intervals have 

 a slight descent with the valley, that of the highest terrace show- 

 ing frequently a very regular slope. On the Connecticut river 

 above Fifteen-miles falls, the upper terrace descends with the 

 valley in forty-five miles from 1,100 to 850 feet above the sea, 

 averaging 5 J feet to a mile. For 120 miles south from these falls 

 to Massachusetts line, the slope is less steep and less regular, 

 desceendins from 650 to 350 feet above the sea. On the Pemi- 

 gewasset and Merrimack rivers, for ninety-six miles, this slope of 

 the highest terrace varies from 15 to 5 feet in a mile, descending 

 from 750 to 160 feet above the sea. 



Upon entering the large valleys, tributary streams of com- 

 paratively narrow channel and rapid descent frequently formed 

 extensive deposits, in the Champlain period, similar in material 

 to the flood-plain of the main valley, but having a greater height. 

 Sometimes upon Connecticut river these deltas, being partially 

 undermined, form conspicuous terraces a hundred feet above the 

 highest normal terrace, which is the remnant of the river's con- 

 tinuous flood-plain. 



Before the thick forest, natural to all parts of the State, had 

 sprung up, the strong north-west winds were in many places 

 sweeping the loose sand from the valleys upward along the hill- 

 sides. These sand-drifts or dunes are found at heights varying 

 from the level of the highest terrace to two hundred feet above it, 

 along the east side of Connecticut and Merrimack valleys and 

 south-east of Ossipee lake. With the clearing away of the forest, 

 they have become again drifted by the wind. 



The greatest widths of modified drift that can be measured in 

 the Connecticut valley, on the west side of New Hampshire, are 

 in Haverhill and Newbury, two miles, and in Hinsdale and Ver- 

 non, two and a half miles wide. The average width is fully one 

 mile. The most extensive bottom-lands on this river are the 

 Upper Coos intervals at Lancaster, and between Wells River and 

 Bradford, Vt., the latter being twelve miles long, and one-half 

 to oue mile wide, including the Lower Coos intervals of New- 

 bury, Haverhill, and Piermont. The largest plains are expanses 



