CO NEW YORK STATE MUSEUM 



by whitish or greenish bands, both parallel with and at right angles 

 to the stratification plane. In the latter case they are seen to lie on 

 both sides of a joint fissure, which indicates that the discoloration of 

 the rock, often extending to an inch on either side of the joint, is 

 due to percolating air and water, the latter probably carrying or- 

 ganic acids in solution. The horizontal bands, often several inches 

 in thickness, are probably similarly discolored portions along lines 

 of greater permeability. 



No fossils have been found in these shales. 



Gray quartzose sandstone. The red shales terminate abruptly and 

 are succeeded by a stratum of gray quartzose sandstone, which is 

 very resistant, and wherever exposed, produces a prominent shelf. 

 This rock varies somewhat in different portions of its exposure, but 

 it averages perhaps 25 feet in thickness. This bed is exposed along 

 the gorge from its mouth to the whirlpool, where it forms a ledge 

 at the water's edge, beyond which it passes below the water level. 

 It is well shown at Niagara glen, where a spring of cool water issues 

 from beneath it, near the water's edge. In the bank on the opposite 

 side, .where a fine section of the rocks of the gorge is shown, this 

 quartzose bed is seen in its full thickness, lying between the red 

 shale below and the shales and sandstones above. The red shale 

 at the water's edge has crumbled away, leaving the quartzose bed 

 projecting from the wall in some cases to a considerable extent. 



The quartzose sandstone usually forms beds of considerable thick- 

 ness in this region, though near the top of the stratum a number of 

 thin beds generally occur. The best exposure for the examination 

 of this rock is in the quarries opened up in the terrace on which 

 the Lewiston tower of the suspension bridge stands. In these quar- 

 ries the sandstone slabs often show smooth surfaces, which generally 

 bear markings similar to those formed by waves on a surface of fine 

 sand. These wave marks are found in most of the sandstones of 

 the Medina group, but they are nowhere in this region so well de- 

 veloped as in the upper thin bedded layers of the quartzose sand- 

 stone. No fossils have as yet been found in the gray sandstone on 

 the Niagara river, though farther east a similar quartzose rock 

 shows shells of the Medina L i n g u 1 a on the surfaces of the lay- 

 ers, which also show wave marks. 



