74 
PALAEONTOLOGY OF NEW-YORK. 
the blackened, 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¬ 
nation, breaking in large pieces, but with numerous faults, the ter¬ 
minations or faces of the faults showing smooth, glazed surfaces, 
while the continuation of the laminm, 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 laminm 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 micaceous 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 band, we not unfrequently find some hard lamina of an inch or more in thickness, tra¬ 
versed by 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 faults 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. 
