184 ERIE DIVISION. 



we have just observed, are sandy ; but they are often interlaminatcd with thin soft slate of 

 a Ijluish or ajreenish color, and all its beds, as a whole, are thin, but rarely even-bedded. 

 The particles too are usually fine, and it is exceedingly rare to meet with coarse conglo- 

 merates ; though near the superior part of the group, a few thin pebbly beds are sometimes 

 observed, and seem to occupy pretty constantly a uniform position. 



Litholoi'ically the Hamilton shales resemble those of the Hudson river. They are 

 usually gray, but sometimes brown from weathering — some beds particularly so towards 

 the top of the series. 



Imbedded or associated minerals. It can hardly be said to furnish any minerals. The 

 beds are rarely (if ever) even sparry in this State. This arises from the perfect quietude 

 which prevailed during the deposition of the beds, and the slight fractures which they 

 suffered at the time of their elevation. The only indication of foreign mineral matter 

 which this grovip discloses, is a thin band of impure carbonate of iron which is occasionally 

 seen in the upper beds. 



Relations of the Hamilton shales. The relations of this mass are nearly the same, both 

 eastward and westward. It reposes every where upon the Marcellus slate. Superiorly 

 the Tully limestone seems to be wanting in Schoharie and Albany counties, and hence in 

 this direction 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 Chemimg. To the west, as has 

 been remarked, the series is restricted by the Tully limestone. It may be that this restric- 

 tion is too artificial and arbitrary, inasmuch 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 introduction 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 would occur if a 

 change of level had taken place in the bottom upon which the former. materials had been 

 deposited. 



..Agricultural 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 lime- 

 stone shales that have been already described. This change is due to the constitution 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 per- 

 haps 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 distantly associated, 

 if the expression is proper, with limestones below. Thus the Utica slate resembles the Mar- 

 cellus slate : both are somewhat calcareous, and both succeed heavy beds of limestone, 

 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, ap- 



