22 SURFACE GEOLOGY. 



Mohawk river, but most noticeably west of the village, extending nearly 

 a mile parallel with the river. Its height is about 70 feet above the river, 

 and 50 above the low alluvium on each side. Its material is the same 

 as that of the long kame farther south in this valley, being principally 

 coarse, water-worn gravel, with abundant pebbles six inches to one foot 

 in diameter. This ridge was deposited in the glacial channel of the river 

 which flowed from the ice-sheet at its final melting. 



We must refer to a similar cause the slightly modified drift in Leming- 

 ton, just north-west from Colebrook bridge; in Columbia, the high gravel 

 terrace north of Sims stream ; thence for a mile southward the moraine- 

 like, level-topped or irregular drift, slightly modified, at about 100 feet 

 above the river ; and the coarse drift ridge on the east side of the river a 

 half mile above Columbia bridge. The last is a distinct ridge, one third 

 of a mile long, parallel with the river, and from 50 to 75 feet above it, 

 being from 25 to 50 feet above the adjoining lowland. This may have 

 been a medial moraine. It contains many angular rock-fragments from 

 two to three feet in size, and seems scarcely modified, appearing like por- 

 tions of the kames along Merrimack river. 



Between Columbia bridge and North Stratford the descent is rapid and 

 the terraces are irregular. At Columbia bridge the highest alluvial banks 

 are 48 feet above the river; at North Stratford, 119. Where the river 

 now descends lOi feet the stratified drift of the valley shows a slope 

 of only 30 feet, or about three feet to a mile. After we pass this steep 

 and narrow portion, and enter a wide valley again where the river is 

 comparatively level, we find the upper terrace falling much more rapidly, 

 or nine feet to a mile. At Groveton it has again descended to a height 

 50 feet above the river. As we approach Fifteen-miles falls, the upper 

 terrace slopes very slowly down to the lower, and they can scarcely be 

 distinguished as separate heights below South Lancaster. The wide 

 river-plain here rises gradually from 5 or 10 to perhaps 20 or 30 feet 

 above the river. 



In Stratford and Brunswick both heights of the alluvium arc well 

 shown, the highway being on the upper terrace and the railroad on the 

 meadow. The former is about 100 feet above the river, and at Bruns- 

 wick Springs, and for much of the way through Stratford, is from one 

 fourth to one third of a mile wide. At Stratford Hollow depot the rail- 



