276 
GEOLOGY OF THE SECOND DISTRICT. 
72. 
The stratum marked with oblique lines, is one clearly distinguished from the other strata. It 
is broken, as is seen in the diagram, into short pieces, and these are elevated in succession 
as they extend south, and at the same time cut off from each other by the veins of calcareous 
spar, some of which are parallel with each other. All the strata have suffered the same 
movement from top to bottom, but the one marked with oblique lines is a stratum of lime¬ 
stone, which is readily distinguished from the slaty ones, and hence becomes easy of refe¬ 
rence. The dark short thick lines are the dykes referred to above ; some portions of them 
are like putty, or paste, and are constantly washing out. Coal seams are dislocated in a 
mode precisely analogous to the stratum of limestone in this cliff, often occasioning great 
perplexity to the miner. 
There are two fossils which appear to be characteristic of the chazy limestone. The 
maclurea already referred to, and a columnaria much resembling the Columnaria sulcata. A 
large species of orthoceratite also is quite common at Essex. The annexed drawings of the 
maclurea (No. 1), and columnaria (No. 2), will convey to the reader the characteristics of 
73. 
these two fossils ; the third figure, which also appears, is a tail of a trilobite belonging to the 
birdseye, the next rock above. 
