SOME GLACIAL WASH-PLAINS. 101 



of eighty feet above the sea and has an average elevation 

 of forty-five feet above the plain on the soutii. It is a 

 complex structnre of glacial materials. The core of the 

 ridge is clay apparently pushed up from the area on the 

 north. On the south side of the ridge, as in the vicinity of 

 French Pond Lane, a sheet of washed gravels declines 

 southward from near the top of the ridge. Locally, along 

 this crest, the southern slope of the ridge is rudely strat- 

 ified as if by the overvvash of waters from ice lying on 

 the north. Just west of the Watertown branch of the 

 Fitchburg R. R., at the point where it i)asses through 

 this morainal ridge, the bulging front of the ridge is 

 strongly morainal in form. 



On top of the clays, throughout the extent of the ridge, 

 is a thin deposit of glacial drift composed of boulders and 

 small fragments derived from the slates and igneous rocks 

 in the Boston area and on the north of it. These materi- 

 als are frequently ice-scratched. 



This ridge is at the southern end of the line of ice-block 

 holes with attendant wash-plains which begins in Fresh 

 Pond and extends northwards through Spy Pond in Arl- 

 ington to the Mystic Lakes, the Winchester Ponds and 

 Horn Pond in Woburn. The moraine bordering Fresh 

 Pond indicates that there was a slight forward movement 

 of the ice on the line of the \Vol)urn-Arlington depression, 

 causing the ice to excavate the underlying clays in Belmont 

 and Cambridge. This movement lasted perhaps somewhat 

 later here than the disappearance of the ice in the drumlin 

 area to the eastward in Somerville. 



Kames on the west side of Fresh Pond, as pointed out 

 by Professor Crosby in 1889, show marked signs of 

 overriding by the ice. The annexed figure represents a 

 sketch of folds in the gravels observed by the writer on 

 June 7, 1891. Further evidence of ice movement in this 



