212 FREDERICK G. CLAPP 



The perfect ice-contact slope along the Boston & Albany Rail- 

 road east of Wellesley Hills, together with the absence of any flat- 

 topped deposits rising higher than 90 feet, throughout the area to the 

 northward, and likewise from the entire region east of the Brookline 

 and West Roxbury highlands, proves that the northern part of the 

 Boston basin was then occupied by the still little- decayed ice-sheet, 

 an arm of which extended up the Neponset valley as far as Norwood. 



PLAINS OF OTHER LEVELS. 



Cedar Hill lakelet. — There still remain to be mentioned several 

 important plains at levels different from any heretofore described. 

 One of these plains occurs on the divide between Noanet and Mine 

 Brooks in Dover. It lies at an elevation of 270 feet, and has a tribu- 

 tary esker on the north and frontal slopes on the south. Beginning 

 a short distance south of the plain, and extending to beyond Walpole, 

 a distance of over four miles, is one of the finest eskers in the region, 

 supposed to mark the course of the stream through which this lakelet 

 discharged. 



Dedham plains. — In the towns of Dedham and West wood are 

 several plains having an elevation of about 120 feet. These are flat- 

 topped, are either entirely or nearly surrounded by ice-contacts, have 

 abundant kettles, and are not known to correspond with plains of any 

 other group. Along the valley of the Charles River, between Dedham 

 and South Natick, are a number of plains at elevations of 100 to 120 

 feet, which may belong to the same stage. Below this elevation all 

 the plains are confined to the Lake Shawmut area, the western limit 

 of which is marked by flat 90-foot deposits north of the ice-contact 

 at Riverside and Newton Lower Falls, and which extend eastward 

 throughout the Boston basin, where they are recognized at all eleva- 

 tions down to sea-level. 



HISTORY OF THE LAKELETS. 



The highest known plain in the region, the Cedar Hill plain, has 

 an elevation of 100 feet above the next lower level, and must have 

 been formed at the time of the earliest uncovering of the pass in the 

 Dover highlands, which left a lake irregular in shape covering an 

 area of nearly one square mile, walled on the east and west by rocky 

 hills, and on the north and south largely by ice. The eskers in the 



