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 1¾ 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.
[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.
Fig. 5. Rocky River Valley. Diagram indicating lowest rock levels which have been discovered by drilling.
At the point marked No. 7+1000, about 1¼ 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.