ile
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.

EFFECT OF GLACIATION

The preglacial history of Rocky River as outlined assumes that before
the glacier covered this part of Connecticut the present lower course
of Rocky River was separated from the rest of the system by a divide
situated somewhere between the present mouth of the river and the
mouth of Wood Creek. It remains to be shown by what process Rocky
River was cut off from its southern outlet into Still River and forced
up its eastern branch and over the col into a tributary of the
Housatonic. Though the preglacial course of Rocky River appears to be
more natural than the present one, it is really a longer course to the
Housatonic; the older route being 32 miles, whereas the present course
is 19 miles. This fact explains, in part, why the glacier had little
difficulty in altering the preglacial drainage, and how the change so
effected became permanent. Eccentric as the resulting system o