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120 J. D. Dana—Phenomena of the Champlain Period. oe 
on the contrary it covers probably an excavation in the subja- 
cent sandstone. On the western margin of the depression, rise — 
the low “ Beaver Hills,” and these are sandstone hills with a 
thin covering of unstratified drift. These hills (see map) have 
the trend of other sandstone hills of the region whose outline 
was plainly determined by the direction of movement of the 
ploughing glacier. : 
No similar soundings have yet been made in the Pine Marsh 
depression. But the fact that the waters are subterranean, and 
its close resemblance to the Beaver Pond depression in all its 
features, are favorable to the conclusion that the two are alike 
in depth of excavation and of one mode of origin. 
As to origin, we have the following basis for a conclusion: 
1. The resemblance in each to the channel of a great river, 
both in width and in steep terrace-fronts. 
2. The depth of the trough :—that of the Beaver Meadows 
extending much below the sea level, as if channeled out of the 
ew Haven sandstone region by the glacier. 
3. The fact that the Pine Marsh depression or channel-way, - 
and Mill River valley for three miles next north, have approx- 
imately the same compass course, coincident with the glacier 
flow, making them one channel-way; and that this channel 
way points directly through the open center of the New Haven — 
region (between Pine and Mill Rocks) nearly toward the head 
of the bay (which bay it is to be noted, is the termination of 
the Connecticut river valley or trough); while the course of 
Mill River below the junction with Pine Marsh Creek makes an 
angle of 40 degrees with that of the glacier-flow, and passes 
through a narrow gap, in trap, at Whitneyville. 
Objections to the conclusion here indicated are apparent (1 
in the abrupt southern termination of the Pine Marsh depres 
sion, and (2) the isolation of the Beaver Pond depression. ae 
Before considering further this question of origin, the facts 
respecting the “ Kettle-holes”’ need to be surveyed. — s 
4. The Positions and Characteristics of the Kettle Holes —The 
kettle holes are nearly seventy in number. Of these, (1) éwenly 
are situated on or near the borders of the Beaver Pond depres 
sion ; (2) thirty, by the Pine Marsh depression; and (8) seven- — 
teen at Augurville, near the junction of Sluice-way Brook with 
Mill River. The map Plate II shows their positions. : 
All occur in the stratified drift ; that is, the well-bedded mate- 
rial of the New Haven plain, or that of the terrace-formation, — 
gravel-made and sand-made portions irrespectively, away 'rom 
all unstratified material, or till. This formation in their vicinity 
has its usual horizontal bedding and flow-and-plunge structure. — 
Whether the horizontal feature usually extends quite to te 
edge of the kettle-hole has not been ascertained, because of 
