Upham. 
40 [March IS, 
these doubtless rei>resent the direction of the ice iiioveineiit here 
during a considerable time in the later part. of the Glacial period. 
In some places, as at the quarries on the south side of Clarendon 
Hill, perhaps an earlier direction of the ice-flow is recorded by 
the south-southwestward striae. The most remarkable deflec- 
tions of the currents, however, causing them to pass east-south- 
eastward or occasionally due east or north of east, over the rock 
hill quarried north of Winter Hill, on Lowell Street, on the 
Lexington branch railroad near Cedar Street, on Willow Avenue, 
and at the City Quarry, appear to belong to the time of departure 
of the ice-sheet from this region, when its motion was turned 
toward an open bay melted into the receding ice-border on its 
seaward side. 
Upon Somerville and all the vicinity of Boston the ice-sheet 
when it extended farthest was probably from 2,000 to 2,500 feet 
thick, increasing in its depth northwai-d and northwestward. Its 
currents here moved at that time to the south and south-south- 
east, but during later stages they vvere deflected to the east- 
southeast or even in some places to a due east course. This 
deflection appears to have been due to the faster melting and 
retreat of the ice from the ocean on the southeast than from the 
land surface of southern New England, whereby a large embay- 
ment was melted out from the border of the ice upon the present 
area of Massachusetts Bay, at last turning the currents of the ice 
here toward that oi)en area on the east. 
To the same time as the eastward deflection of the glacial striae 
we must refer the accumulation of the many drumlins in Somer- 
ville, Boston, Cambridge, Everett, Chelsea, Revere, and 
Winthrop, where the longer axes of these massive oval hills of 
till trend prevailingly to the southeast and east-southeast, while 
the striation on the bed-rocks is mostly south-southeast, differing 
from the trends of the drumlins by 25 to 45 degrees. For ex- 
ample, the altitudes (above mean tide sea level) and trends of 
the ten drumlins in Somerville are as follows : Asylum Hill, 58 
feet, S. 45° E. ; Convent Hill, original top before grading, 94 
feet, S. G5° E. ; Winthrop Hill, on "Ten Hills farm," close 
southwest of the Middlesex Avenue bridge, 65 feet, S. 60° E. ; 
Prospect Hill, origiuid top before grading, 133 feet, S. 45° E. ; 
Central Hill, 109 feet, S. 60° E. ; Winter Hill, 141 feet, S. 70° E. ; 
hill on Beacon Street close southeast of Washinsjton Street, 34 
