84 
AMERICAN GEOLOGY. 
the great extent of the sedimentary limestones it will follow 
that these must have been formed from preexisting limestones, 
which once belonged to the original constitution of the earth’s 
crust. We must go back to their primary condition and posi¬ 
tion in the earth’s crust. No one at the present day pretends 
that limestone is an organic product in the strict meaning of 
the word. Is it not better, then, when we find a limestone occu¬ 
pying those relations which forbid the adoption of the view 
that it is a changed rock, to place it with those masses with 
which it is associated? And such is the position and relation 
of all those masses of limestone which I have described under 
this head, that they can not be referred to the Silurian system 
without doing unnecessary violence to the relations which they 
naturally sustain. 
SERPENTINE. 
§ 65. It is green; the variety of shades being numerous, 
passing into black on one side, and on the other into very pale 
green. It is sometimes brown. Its grain is always fine, and 
in this respect there is a very great uniformity in all its varie¬ 
ties. It is never coarse like certain varieties of limestone, and 
if columnar, as at Lowell and Newfane, Vt„, and Middlesex and 
Cummington, Mass., the individuals are extremely slender, 
passing into asbestus. The rock is homogeneous, and is both 
massive like granite, and laminated like gneiss, and hence be¬ 
longs to both divisions of the pyrocrystalline rocks. The mas¬ 
sive kinds occur at Lowell and Newfane, Vt., and Middlefield, 
Chester and Blanford, Mass.; or it may be it is sometimes 
obscurely laminated. The distinctly laminated kind in Macon 
county, N. C., is of a dark green, where its lamination is more 
distinct than that of gneiss. The same variety is found at or 
near Port Henry, Essex co., N. Y. In Middlefield and Chester, 
it forms a range of hills some five or six miles in length, and 
less than half a mile in breadth. The serpentine of the Bare 
hills, near Baltimore, resembles that of Chester, and is proba¬ 
bly more extensive. This rock is remarkably distinct from 
