iS94. 
213 
[Wondwnrtli 
ESKEK POXDS (TakNS) AND SwAMPS. 
The surface skirting the base of an esker is frequently depressed 
below the adjacent region. Where the depression is lower thiui 
the level of the water-plane of the gravels which border the 
esker, the hollows become the seat of small ponds or tarns. 
Compounce Pond, south of Bristol, Conn., and Cunliff's Pond, 
below Providence, R. I,, are examples shown on the atlas sheets 
of the U. S. geological survey. The ponds of this class are 
usually narrow or elongated parallel with the esker, and form an 
insignificant but common group. Where shallow, they have for 
the most part been converted into swamps during the postglacial 
epoch. Examples occur associated with the Auburndale esker 
ami other ridges. 
The ponds and swamps may tiank both sides of an esker. In 
Cunliff's Pond, the water overflows a low place at the northern 
end of the esker, thus washing both sides of it. A conspicuous 
instance of this class of ponds occurs in the course of the Black- 
stone River near Pawtucket, R. I., at Lonsdale, associated with 
the esker described on p. 204. The ponds in this case are flanked 
on the east and west by well-developed terraces of the class 
denominated "lateral moraine terraces" by Gilbert. It is obvi- 
ous that the depressions occupied by the pond are not due to 
Fig. 5. Generalized section across meridioual valley with lateral 
moraine terraces (or hillside karaes), with medial esker, showiui? sym- 
metry due to deposition of sands and gravels in the presence of melting 
valley-tongues of the ice-sheet. A A, ice-sheet previous to the stage BB, 
when isolated blocks hold open cavities between the esker and tlie ter- 
races, E E. C is the tunnel in A A in wliich the esker originates. 
D D, esker ponds or swamps. 
