GLACIO-AQUEOUS ACTION IN NORTH AMERICA. 199 



but the hills are low, rarely more than one hundred or two hun- 

 dred feet high, and the slopes very gradual. The village in 

 Andover, around the Theological Seminary, stands upon one of 

 these broad swells of land ; and about half a mile west of the 

 seminary, a small stream, two or three rods wide, called the 

 Shawsheen, runs northerly towards the Merrimack. On each 

 side of this stream, the land rises very gently for some hundreds 

 of rods. And it is upon the west side of the river that these 

 remarkable ridges occur. They all consist of long narrow ridges 

 of gravel, or sand, having a nearly equal slope upon each side. 

 One of them is well known in Andover, under the name of 

 Indian Ridge; and being for a considerable distance covered 

 with pines, it forms a romantic path for literary peripatetics. In 

 company with Rev. Alonzo Gray, of Andover, I traced this ridge 

 towards a mile and a half, interrupted only occasionally by a 

 road, or a brook, or other slight depression. This ridge is shown 

 on the Map of Moraines in Andover, PI. IX, e!xtending from A to 

 B. When we examined it, we supposed, that after a considerable 

 interruption between B and O, it continued to F, where it was 

 covered by a deposit of sand, forming a sandy plain. But sub- 

 sequent examination has satisfied Mr. Gray, that this Avestern 

 part of the ridge (O F,) continues southerly as far as E ; and in 

 general, he says that this Western Ridge is on an average fifteen 

 feet higher than Indian Ridge, though of the same general char- 

 acter. He has also traced an East Ridge, branching off from the 

 Indian Ridge at C, and running northerly to D, one huncbed and 

 eighty-five rods. These three ridges he has taken the pains to 

 survey with a chain and compass ; and from his minutes they 

 are laid down on the accompanying map. The ridges repre- 

 sented at G, H, L, M, and N, are placed upon the map without 

 being surveyed ; and they merely indicate that moraines of some 

 extent exist there, and possibly they may have some connection 

 with the three ridges above described. But until they shall have 

 been surveyed and placed in their exact position upon the map, 

 it will be unsafe to found any inferences upon them. They were 

 not surveyed for want of fime. 



The height of Indian Ridge above Shawsheen river, varies 



