Figures 3 and 5 show what is known of the buried channel of Rocky
River. The only definite information as to rock levels is that derived
from the drill holes made by R. E. Dakin for the J. A. P. Crisfield
Contracting Company in connection with work on a reservoir for the
Connecticut Light and Power Company. Numerous holes were drilled at
the points indicated on fig. 5 as No. 8, D, J, No. 7+1000, and No. 7,
but only those showing the lowest rock levels need be considered. In
the following account the elevations quoted are those determined by R.
E. Dakin which differ, as shown in fig. 3, A, from those of the New
Milford atlas sheet.
Between the mouth of Wood Creek and Jerusalem bridge holes made near
the river show that the depth of the drift--chiefly sand, gravel, and
clay--varies from 45 to 140 feet. The greatest thickness of drift,
consisting of humus, quicksand and clay, is 140 feet at a point 20
feet from the east bank of Rocky River and about 1-3/4 miles north of
the mouth of Wood Creek (fig. 5, D). Although some allowance should be
made for glacial scouring, the rock level at this point, 244 feet, is
so much lower than any other record obtained between this point and
Danbury that one is obliged to assume a buried channel with a level at
Danbury at least 75 feet below the rock level found in the lowest well
record.[7] It is probable that this well is not situated where the
rock is lowest, that is, it may be on one side of the old Still River
channel.
[Footnote 7: Well of J. Hornig, rear of Bottling Works, near foot of
Tower Place, 35 ft. to rock, indicated at _a_, fig. 5. The well of
Bartley & Clancey, 94 White Street, 70 ft. to rock, is also
indicated at _b_, fig. 5.]
The level obtained at No. 8 is from a hole drilled within 50 feet of
the river. The drill struck rock at an elevation of 316 feet after
passing through 69 feet of quicksand, gravel, and till. This is
clearly not within the channel as it is quite impossible to reconcile
the figure with that at D, less than a mile distant.
South of Jerusalem bridge at J, 150 feet from the river, a hole was
bored through 95 feet of clay, sand, and gravel before striking rock
at an elevation of 298 feet.
[Illustration: ~Fig. 5.~ Rocky River Valley. Diagram indicating lowest
rock levels which have been discovered by drilling.]
At the point marked No. 7+1000, about 1-1/4 miles from the mouth of
Rocky River, the evidence derived from 8 drill holes, bored at
distances ranging from 200 to 550 feet from the right bank, shows the
drift cover to be from 48 to 72 feet in thickness. At 200 feet from
the river the drill passed through 72 feet of sand, clay, and gravel
before striking rock at 303 feet above sea-level.
At No. 7, about one mile from the mouth of Rocky River, a hole drilled
415 feet from the right bank showed 58 feet of drift, consisting of
clay, sand, gravel, and boulders. The drill reached rock at 342 feet,
which is the figure given by R. E. Dakin for the elevation of the
river at this point. Drill holes made, respectively, at 50 and 60 feet
to the right of this one showed a drift cover of 61 feet, so that the
underlying rock rises only 4 feet in a distance of 475 feet to the
east of the river.
The foregoing evidence, showing a rock level at D 98 feet lower than
that at No. 7, leaves no doubt that the preglacial course of Rocky
River was to the south from No. 7, and there is nothing in the
topography between Jerusalem and Danbury to make improbable the
existence of a buried channel.