Wood worth.] 214 [Feb. 7, 
excavation by the river, but rather to the occhision of sediments 
througli the presence of masses of ice, having, at the time the 
deposition of the terraces ceased, the cross-section of the cavities 
now occupied by the ponds. This is but one of many instances in 
which it appears that the ice lingered longest near the sides of 
eskers. The annexed diagrammatic cross-section is typical of 
this class of facts. In fact, the existence of the group of esker- 
ponds and swamps depends altogether on this circumstance. 
There are many reasons for believing that tongues of ice lay in 
the deeper valleys of southern New England when the uplands 
bordering them were practically bared of the glacier. The ice 
remained in the valleys longest because it was there thickest and 
took longest to melt. It was further preserved in these situations 
by the gravel and sand dejDosited on and about it. Another pos- 
sible reason for the ice remaining longer in contact with eskers is 
the protection afforded by the esker itself, for a subglacial channel 
with its gravel filling would be more likely to retain the ice than 
a channel, either an ice-canon or a superglacial way, open to the 
sun's heat and the influence of superficial running water. The 
water flowing in subglacial channels is necessarily cooler than the 
possible tem])erature of superglacial streams. 
The eskers of this district appear to have been deposited when 
the ice-sheet had dwindled to the dimensions of stagnant, melting 
remnant glaciers. From this circumstance arose the frequent 
symmetry observed in the distribution of lateral terraces con- 
fronting either slope of an esker. The symmetrical distribution 
of deposits about the esker at Lonsdale, R. I., and Cunliff's 
Pond, in Providence, illustrates this feature. 
Eskers and Glacial Lobes. 
When the retreating ice-sheet of the last glacial epoch had its 
front still in southern New England, there were at least three 
glacial lobes, viz., (\) the Cape Cod lobe, (2) the Narragansett 
Bay lobe, (3) the Connecticut River lobe. The morainal 
deposits connected with the lobes are most distinct on the east. 
The loops of the accumulations have already been outlined by 
Chamberlin.^ Inside and northward of the frontal de})Osits of 
iTIiird Annual report U. 8. gcol. surv. 
