HAMILTON SHALES. 
185 
pear towards the end or about the middle of the series. So in the Hamilton shales, im¬ 
pure calcareous bands are met with, though the calcareous matter seems to have been 
derived from the petrifactions which they inclose. This shows that some calcareous mat¬ 
ter existed in solution in the waters from which these rocks were separated or deposited ; 
indeed, the shales sometimes effervesce feebly. Now the main peculiarity which we find 
in these rocks, consists in the ability to produce good pasturage : the soil possesses that 
light character which fits it for sweet grazing. There is always seemingly sufficient alu- 
mine or clay in these rocks to give the debris the proper consistency to hold water, and 
this rarely to excess. There are two other circumstances which contribute to form a 
grazing country where these rocks predominate, namely, sweet or pure water, and a hilly 
surface. The water, under such circumstances, drains off rapidly, and leaves the soil 
refreshed : it will not stagnate above or beneath the surface. If the grass and herbage is 
not so luxuriant, it is sweeter, and promotes the health of the animals which feed upon it. 
The atmosphere circulates freely over the hills and through the valleys, and thereby 
rapidly renews the essential elements of life and activity. 
Succession of strata and, illustrative views . The succession of the groups and strata are 
well exposed on Cayuga and Seneca lakes, and in the valley of the Schoharie (See Plate 
xxi., sections 3 and 4 ; or Plate xx., sections 2, 4, 5 and 6). For illustrative views, see 
Plate vi., which may be compared with Plate iv. : the formations of the former are un¬ 
disturbed, while the latter is on a zone or belt which has been broken up by internal 
convulsions. 
Thickness of the Hamilton shales. It is difficult to obtain the data from which the thick¬ 
ness of this rock can be determined. By estimating the fossiliferous and non-fossiliferous 
parts by themselves, and summing up the result, we obtain from 1000 to 1200 feet thick¬ 
ness. In the eastern part of the State, in Albany and Schoharie counties, the thickness 
appears to be much greater than in the western counties; at the same time it must be 
acknowledged that the line of demarkation between this and the upper part of the Erie 
division is indistinct, and hence masses which belong properly to the Devonian or Catskill 
rocks may be included. The lower part of the Hamilton shales are destitute of fossils in 
Schoharie county, for about fifty feet: then we meet a band of fossils, among which is a 
Conularia and Posidonia ; this is succeeded by another non-fossiliferous band of conside¬ 
rable thickness, and then fossils again occur; and in the Olive shales, so called, the fossils 
are very numerous, and among them we find a great abundance of the Delthyris mucro- 
nata , the beautiful Orthonata undulata , and Dipleura dekayi. Still higher in the series, 
we find an abundance of vegetable fossils, which extend through beds of sandstone and 
shale for sixty or seventy feet; and lastly, in the tops of the hilly region of Fultonham in 
Schoharie, the rock becomes a grayish sandstone, with stems of plants, encrinites, and a 
large delthyris. In the hills of Fultonham, the thickness of the superimposed masses is 
at least eight hundred feet. The beds are thin at the base, but not even-bedded ; at the 
[Agricultural Report.] 
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