166 View of the Head of the Gorge at Summit. 
same, both eastward and westward. It reposes every where upon 
the Marcellus slate. Superially the Tully limestone seems to be 
wanting in Schoharie and Albany counties, and hence in this di- 
rection the line of demarkation is not well defined. The shales run 
into and are imperceptibly incorporated with the next series of 
rocks, which are known abroad by the name of Devonian, and in 
this state by that of Portage or Chemung. To the west, as has 
been remarked, the series is restricted by the Tully limestone. It 
may be that this restriction is too artificial and arbitrary, inas- 
much as the same mineral characters are preserved, and also some 
of the fossils; and it is hardly possible to find any where those 
physical changes which sometimes appear, and mark the introduc- 
tion of a new epoch. Some of the beds, towards the upper part, 
are less regular, more concretionary, and appear as if they were 
deposited under a slight change of circumstances, such as w^ould 
occur if a change of level had taken place in the bottom upon 
which the former materials had been deposited. 
Jlgricultural capacity of the Hamilton shales. — We are now 
introduced into a region, whose capabilities in production are 
decidedly of a different kind from those of the limestone shales 
that have been already described. This change is due to the con- 
stitution of the rocks mainly, although we have no doubt that 
height, configuration, and slope, may modify to a certain extent 
the productive capabilities of the region over which these rocks 
extend. Agriculturally they closely resemble the Hudson river 
rocks, and we may perhaps say with truth, that this resemblance 
is no less than that of their lithological characters. Both series 
are remarkably destitute of calcareous matter, and both are dis- 
tantly associated, if the expression is proper, with limestone be- 
low. Thus the Utica slate resembles the Marcellus slate; both 
are somewhat calcareous, and both succeed heavy beds of lime- 
stone, which constitute important landmarks or wayboards for the 
determination of series and groups. In the Hudson river shales, 
a few bands of limestone, highly fossiliferous, appear towards 
the end or about the middle of the series. So in the Hamilton 
shales, impure calcareous bands are met with, though the calca- 
reous matter seems to have been derived from the petrifactions 
which they inclose. This shows that some calcareous matter ex- 
isted in solution in the waters from which these rocks were sepa- 
rated 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 alumine 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 
