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MANHATTAN ISLAND
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Rivers, and on the west into the Hudson River. The Hud­son River thus becomes a very old, a pre-Silurian, river cut­ting its way to the ocean in a gorge, perhaps accentuated by falls and rapids, with probably equally picturesque tribu­taries.
Borings made by the Board of Water Supply of New York City, in connection with the project of bringing water from the Catskill Mountains, have shown the existence of numerous deeply buried channels representing pre-glacial stream courses. Many of them indicate channels cut far below present sea-level at considerable distances back from the Hudson River. From engineering records it appears that the depth to bed rock in the Hudson River has never been determined at any point in its lower course. Profiles of supposed rock-bottom based upon wash-borings have been proven by the recent work to represent simply the bottom of the finer silt filling. The re­sults show that more than 200 feet of more compact material lies below this silt at the point now being tested, and that the rock bottom of the ancient Hudson lies more than 450 feet below the present river level throughout a large part of its lower course. (C. P. Berkey.)
This assumption involves, of course, a much higher eleva­tion of the whole coast. As far as the Hudson River is con­cerned, the next problem it presents is its historical relation to the Triassic beds west of it in New Jersey (Newark for­mation) and the Palisade escarpment. Geologists agree that the Palisade dike is intrusive, ins., was inserted in overlying beds of sediments, and we must assume a depression for their accumulation in the brackish water (Eastman) trough or basins of the Triassic deposits, which depression, however, did not submerge the meridional ridges of Manhattan Island and western Connecticut. Again, elevation supervened, and at this point it seems necessary to intercalate a fault line, per­haps, on the west margin of the Hudson River channel to give differential prominence to the Triassic shales, sandstone, and