MODIFIED DRIFT ALONG MERRIMACK RIVER. 99 



rimack group. The kames of Nashua and Hudson differ in the same 

 way in respect to their material from those farther north. South of the 



Fig. 23. — Section in Nashua and Hudson, i mile """""^ ^^^• 



NORTH FROM THE MOUTH OF NASHUA RiVER. 



Length, 2 miles, 

 till mentioned three terraces occur. The middle one corresponds in 

 height to the extensive plain of the south part of the city, which is 150 

 feet above the sea, or 57 feet above Merrimack river. This plain aver- 

 ages two miles in width for three miles west from the Merrimack, to 

 Mine falls on Nashua river. It lies mostly on the south side of this river, 

 and also includes the last three miles of Salmon brook within its area. 

 The water-power of Nashua is supplied by these streams, the utilized fall 

 of Nashua river being 51 feet, and that of Salmon brook 57 feet. 



The origin of the material of this plain was partly from each of these 

 streams and partly from the north-west, along the avenue followed by the 

 Wilton Railroad. Salmon brook has considerable alluvial deposits along 

 its whole course. Very interesting kames occur along this brook in Dun- 

 stable and in Groton, Mass. They extend several miles, lying north and 

 south, and are well seen from the Nashua, Acton & Boston Railroad. It 

 appears that these were formed when this was one of the principal outlets 

 from the melting ice-sheet. After the full disappearance of the ice the 

 direction of drainage was changed, and a part of the deposits of this area 

 has been carried back northward by this brook. 



Main street in Nashua, at the city hall and at the Worcester depot, has 

 the same height with the dam at Mine falls (152 feet above the sea). 

 The descent of the plain eastward in this distance is about 20 feet. 

 Three miles farther south-west, upon the Nashua river in HolHs, we find 

 plains 50 feet higher, or 70 feet above the river, which has a wide alluvial 

 area on both sides to Massachusetts line. Kames, which were probably 

 formed by waters flowing south from the melting ice, occur in Nashua 

 just north of Hollis station, and on the east side of the railroad at the 

 next crossing to the north ; and others, previously mentioned, lie near the 

 river, a mile farther north. One of the finest displays of kames to be 



