BOUNDARY OF THE GLACIATED AREA. 139 



and bowlders which have been scraped off by the ice from 

 the mountains and ledges of New Hampshire and the inter- 

 vening portions of Massachusetts, transported to the glacial 

 margin, and there deposited in such quantities as to consti- 

 tute the whole southeastern portion of the latter State. The 

 three hundred and sixty lakes of Plymouth township are 

 nothing else than a cluster of kettle-holes. Manomet Hill, 

 southeast of Plymouth, is not a mountain which has been 

 thrust up by convulsive agencies, nor yet a remnant of a par- 

 tially eroded plateau, but a glacial deposit, hundreds of feet 

 in height and many miles in extent. From the fact of its 

 running nearly at right angles to the backbone of Cape Cod, 

 Manomet Hill is spoken of by some as a medial moraine. 

 But it is doubtful if it is necessary so to regard it. The re- 

 treat of a glacier, like the retreat of an army, is determined 

 in part by the nature of the opposing foe. In the present 

 instance there are abundant reasons for believing that the ice 

 retreated by the left flank ; for it is evident that the ocean 

 had much to do in setting bounds to the general southeastern 

 movement of the ice-sheet in New England. From the con- 

 tour of the coast, it can be seen at a glance that the waters of 

 the ocean had constant opportunity to eat in upon the ice 

 from the east as well as from the south. 



Nantucket marks the extreme southeastern limit. Here 

 the ice maintained its position against opposing forces, until 

 the outer line of moraines just mentioned was built up. The 

 next line of defense taken up by the ice is that marked by 

 the backbone of Cape Cod. The retreat had been farthest 

 on the side most exposed to the ocean, and hence the dis- 

 tance between the moraine of Nantucket and that at South 

 Brewster is much greater than the distance between Martha's 

 Vineyard and ^Wood's Holl. The next line of defense taken 

 up by the ice-front along the course of Manomet Hill, left 

 Cape Cod and the whole shore of eastern Massachusetts open 

 to the undisputed sway of the ocean. 



The two lines of moraine so clearly marked in south- 

 eastern Massachusetts can be readily traced westward through 



