The Falls of Niagara and Other Famous Cataracts

by George W. Holley

CHAPTER VII.

Composition of the terrace cut through—Why retrocession is possible—Three sections from Lewiston to the Falls—Devil's Hole—The Medina group—Recession long checked—The Whirlpool—The narrowest part of the river—The mirror—Depth of the water in the chasm—Former grand Fall.

The water having laid bare the face of the mountain barrier from top to bottom, we are enabled to examine the composition of the mass through which it slowly cut its way. After removing the thin plates of the upper stratum, as we descend, according to Professor Hall, we find:

1. Niagara limestone—compact and geodiferous.

2. Soft argillo-calcareous shale.

3. Compact gray limestone.

4. Thin layers of green shale.

5. Gray and mottled sandstone, constituting with those below the Medina group.

6. Red shale and marl, with thin courses of sandstone near the top.