WESTERN DISTRICT. 
277 
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Which compose the rocks whose analyses we have just given. From the Niagara lime¬ 
stone, upon which the red shale and marl repose* up to the Oriskany sandstone, the mate¬ 
rials are all extremely fine, excepting a thin sandy band near the top of the red slate. 
For seven or eight hundred feet, then, the rocks which form a large body of soil are in 
that condition as it regards size, which fits them for the most effectual action of the roots 
of plants, and for the solution so necessary to prepare them to be received into the texture 
of the plant. The fineness is not such as to pass readily into an impalpable state ; such, 
for instance, as is at all liable to pack, and thereby exclude air and moisture. We regard 
the condition we have here described as quite desirable for wheat, and all other crops 
which admit of high cultivation. 
The origin of the materials constituting these shaly rocks can not be determined with 
certainty. That they were not the immediate result of abrasion from primary rocks is 
certain, inasmuch as their fineness could not have been effected by such an operation, 
unless indeed the materials should be regarded as having been transported far from their 
parent rock ; and, besides, we are unable to detect, by a common microscope, any grains 
of felspar or mica, or the products of any primary rocks, except fine rounded grains of 
quartz. A fact which bears upon the question under consideration, is, that no fossils are 
known in the red and green shales, those deposits which are so exceedingly fine ; and 
this fact seems to favor the view that the deposition actually took place in a deep sea, at a 
depth at which organic beings are not known to exist. 
The rock, which succeeds the Onondaga limestone, is the Marcellus slate ; and it is so 
closely related to the shales below, that its composition may be given in this place. The 
rock is of course thin-bedded and liable to disintegration, and is therefore usually con¬ 
cealed at its outcrop. It is calcareous in many places, and at some points it appears that 
an unusual quantity of lime was deposited with the slate, as a large quantity of septaria 
is inclosed between the layers at such places ; at other places, thin bands of limestone 
appear. 
The shales, in their most common condition, are composed of the following substances ; 
Water of absorption_ 2 ‘00 
Organic matter_ 2-25 
Silex..48 02 
Peroxide of iron and alumina. 10*00 
Carbonate of lime. 36*60 
Magnesia_ 1*00 
100*07 
The vegetable or organic matter is quite as abundant as in the green shales, but it is more 
carbonaceous, or charred, and hence the dark color under which the rock usually appears. 
Sometimes, however, the dark color is due to the presence of decomposing pyrites. 
The passage from the Marcellus shales to the Hamilton group is easy, and is effected 
by an increase of siliceous matter in a coarser state ; besides this change, we may often 
