1893-] 41 
[Upham . 
feet, S. 4o° E. ; Spring Hill, 138 feet, S. G0° E. ; Clarendon Hill, 
whose toj) on Fairmount Avenue is a drumlin mass of till, 90 
feet, S. 50" E. ; and Walnut or College Hill, lying mostly in 
Medford, 155 feet, S. 50° E. 
Elsewhere in all the districts characterized by abundant drum- 
lins in this country and the British Isles, their longer axes and 
the striae are parallel ; and it seems sure that both were deter- 
mined by the currents of the ice-sheet. Their difference in 
direction in the neighborhood of Boston was doubtless due to a 
deflection of the motion of the ice here during its final melting, 
of Avhich we now have ample evidence from these deflected 
glacial striae in Somerville, and from others, apparently more 
rare and local, recorded on Cape Ann by Prof. N. S. Shaler^ 
and in Nantasket and Cohasset by Prof. W, O. Crosby.- Prob- 
ably further examples of eastwardly deflected striae will be 
detected by thorough search in all the cities and towns bordering 
Boston harbor and reaching northeastward to Cape Ann. 
Through the time of its maximum thickness and extent the ice- 
sheet moved south-southeastward across this area, and reached 
to the terminal moraine of Long Island, Block Island, Martha's 
Vineyard, and Nantucket ; and onward the course of its border 
was [H-obably east-northeast along the submarine i)lateaus of the 
Fishing Banks. But when a mild climate began to cause the 
glacial boundary to recede northward, the melting probably ad- 
vanced faster on the aiea of the Gulf of Maine than in southern 
New England, so that the ice-front became indented by a deep 
embayment east of Massachusetts, toward Avhich the latest cur- 
rents along the coast were deflected. The formation of the 
drumlins about Boston seems to have taken place wholly during 
the time of deflected glacial movements, the ground moraine 
being massed in these hills on account of inequalities in the force 
and direction of the overriding ice-sheet, when its receding 
border may have been only a few miles distant. In my previous 
papers on the drumlins of our district read before this Society in 
1879, 1888, 1889, and last November, this relationship of the 
drumlins to the recession of the ice-sheet has been indicated as 
})robable, of which the discovery of these abundant deflected 
striae supplies strong confirmation. 
' U. S.geol. survey. Ninth annual report, for 1887-'88, p. 557, 558, pi. 75. 
2 Boston see. nat. hist., Occasional papers, 1893, v. 4, p. 141. 
