NIAGARA GROUP. 
93 
numerous and regular than any thing of this kind. The following woodcut is an illustration, 
reduced one half, from a specimen from this locality 
29 . 
Concretionary structure in the strata south of Loclport. 
It will be observed that these elevations arc not all circular, but often confluent, forming 
little rounded ridges, sometimes several inches long, and again interrupted. The knobs in 
like manner are often arranged in lines, and they not unfrequently present themselves in 
quincunx order. 
I have seen an instance in the same rock where several knobs became enlarged and much 
elevated, breaking through the superincumbent laminae ; and the surface of the shaly matter 
at the junction presented the smooth and striated appearance common, where one hard surface 
moves over another, as in the sides of faults in strata. 
At Porter’s quarry, one mile east of Niagara Falls, the structure, though somewhat different 
from that of the same strata at Lockport, exhibits the influence of similar causes. The whole 
is thin bedded, and arranged in curved or dome-shaped layers, the ends bending downward, 
and continuing for many rods with the same regularity as in the figure. In some instances, 
for a short distance, the layers are much more abruptly curved than in this illustration. 
