74 . PAL-EONTOLOGY OF NEW-YORK. 



tlie blftckened, shining, and sometimes striated surfaces, more or less 

 conspicuous. The mass presents an appearance as if there had been a 

 movement within itself, or as if it had been partially crushed by the 

 folding, producing a sliding of the fragments over each other. This 

 condition is not universal ; and some portions still retain their lami- 

 ijatioi), breaking in large pieces, but with numerous faults, the ter- 

 minations or faces of the faults showing smooth, glazed surfaces, 

 while the pontinuation of the laminae, if traceable, is not found in the 

 same line ; and an intermediate space is often filled with soft, crushed, 

 shaly matter. Calcareous seams often accompany this condition of the 

 shales. At the same time the heavier arenaceous and argillo-arenaceous 

 layers become harder and more compact, changing somewhat in color, 

 and- developing crystalline matter in the joints*. 



Still nearer to the mountain range the same shales are more broken, 

 and changed in color ; while between the laminae we observe shining 

 particles of a talc-like substance, and finally this becomes a predomi- 

 nating feature. 



In the same stages of progress, the limestones gradually lose their 

 dark color, and numerous ramifying veins of calcareous spar traverse 

 the mass. The fossils lose the definiteness of their forms, and often 

 become much distorted. In the impure limestones we soon find nume- 

 rous, shaly and micapeous interlaminations, and the mass gradually 

 assumes a crystalline structure. Still, long after the crystalline texture 

 becomes marked, the weathered surfaces may show the remains of 

 fossils, the fragments of Crinoidea being among the last to disappear. 



• In the careful study of the strata, when in this condition, for the purpose of tracing some thin 

 fossiliferous hand, we not unfrequently find some hard lamina of an inch or more in thickness, tra- 

 versed hy several faults in the space of a few inches. Sometimes these faults are not more than an 

 eighth or a quarter of an inch, and are not unfrequently seen to affect one-half of a specimen, dying 

 out in the space of a few inches. Again, these &ults are of the extent of an inch or more, and not un- 

 frequently a hard slaty layer of one or two inches in thickness is entirely cut off by such faults, 

 and the parts separated by soft shaly matter thrust in between them. In some parts of the folding 

 or axis it is often difficult to follow these harder layers in their frequent fracturing and displacement, 

 obscured by the intervention of the softer matter. 



