276 



GEOLOGY OF THE SECOND DISTRICT. 



The stratum marked with obhque hnes, 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. 



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■'"••AWVSii.v.W*^'^" 



,:f 



these two fossils ; the third figure, which also appears, is a tail of a trilobite belonging to the 

 birdseye, the next rock above. 



