NIAGARA FALLS AND VICINITY 91 



beds with the bryozoan weathered out in relief on their surfaces, 

 may be found at the base of the cliff in the cut north of the tunnel. 



3 In the northern end of the section the sandstones and sandy 

 shales have a thickness of about 5 feet, and are in turn succeeded 

 b>y 6 feet of shale, weathering readily into a clayey earth, which ac- 

 cumulates, as a talus on the underlying sandstone ledges. As 

 in the other shale cliffs, so here weathering causes a more rapid 

 retreat of the shale than of the overlying sandstone, which therefore 

 projects beyond the shale cliff till it breaks down. 



These shales are mostly gray, sometimes greenish gray, with oc- 

 casional sandstone bands. Toward the top they become intercalated 

 with reddish bands, and finally the prevailing color of the shale be- 

 comes red. 



4 Following these shales is a mass of sandstone from 35 

 to 40 feet thick and consisting mostly of beds which vary from 

 4 to 6 inches in thickness. The sandstone is compact and solid, 

 reddish in color or gray mottled with red. The beds are separated 

 by red shaly partings, with occasional beds of red shale 2 to 4 feet 

 thick. About 20 feet above the base of this sandstone mass is a 

 concretionary layer from 1 to 2 feet thick, which appears not unlike 

 a bed of large rounded boulders. These concretions vary in size 

 up to 3 or 4 feet in greatest diameter, and they lie in close juxta- 

 position, not infrequently piled on each other, thus still more 

 simulating the blocks of a boulder bed. 



This sandstone cliff is in general quite perpendicular, and the 

 thin and comparatively uniform layers, which are regularly divided 

 by vertical joint fissures, produce the appearance of a vertical wall 

 of masonry, for which many people, seeing it only from the rapidly 

 moving train, have no doubt mistaken it. The regularity 

 of these successive beds is at times interrupted by a heavier layer, 

 either red or gray and mottled, which may be traced for some dis- 

 tance, after which it thins out and disappears. This thinning out 

 of the layers in one or another direction is a common and charac- 

 teristic feature of these sandstones, and is a direct result of the ir- 

 regularities of current action during the deposition of the sands. 

 We may trace a sandstone mass for some distance, and then find 



