156 GEOLOGY OF THE SECOND DISTRICT. 



This arrangement produces a complication in the geological structures of this system, that is 

 quite perplexing. If the granular quartz is left out of view, however, and we consider it as 

 occurring in accidental beds, a great part of the difficulty is removed. I shall have occasion 

 hereafter to speak of these masses or beds of quartz, which are so anomalous in this for- 

 mation. 



In consequence, as it would appear, of the ready disintegration of the limestone, it always 

 forms the floor of the valley, and the slates the mountain masses. Where the latter present 

 to the weather their edges, they not only resist the action of the air, and of moisture, frost, etc., 

 but also form a strong barrier to limit the action of floods and currents ; but limestone, espe- 

 cially when mixed with silcx or magnesia, is readily acted upon by atmospheric agents. 

 There appears no method by which to account for the position of the limestone, other than 

 the one here ofi"cred ; for originally, there can be but little doubt, the latter rock was coexten- 

 sive with the slate. The valleys furnish themselves evidence of having been formed by denu- 

 dation, at least in part ; and as the slates, from their peculiar structure and position, are 

 capable of resisting chemical and mechanical forces to a much greater degree than limestone, 

 they remain in mountain masses, while the limestones have been perfectly furrowed and 

 worn down to their present level. Other rocks, as granular quartz, when lying in the midst 

 of limestone, have also remained, forming high hills, while the hmestone at the base on 

 both sides appears in the lowest depressions of the valley. This is the case around the base 

 of the hill in Williamstown, Mass., known locally as Stone hill. In the valley of Berkshire, 

 instances of this nature are common. 



Valleys of Berkshire, and water drainage. 



In the preceding remarks, I have omitted the limestone which lies in Williamstown, at and 

 upon the cast base of the Taconic range, for the reason that some doubts exist whether it is 

 really distinct from that which underlies the middle part of Hoosic valley, or not. It is sepa- 

 rated from it by the mass of granular quartz which forms Stone liill, and dips beneath it. It 

 is a mass three hundred feet thick ; and in the same range, one mile north, a similar bed 

 appears, which is probably the same prolonged in this direction ; so, to the south, this same 

 bed appears to continue, taking the course of the valley of the west branch of Green river 

 which comes from Hancock. If this mass of granular quartz was continuous, there would not 

 be so much uncertainty in regard to the different beds of limestone. When, however, we 

 find the limestone of tlie middle part of the Hoosic valley commingling, as it were, with this 

 lateral and western bed of limestone on reaching the south end of Stone hill, all the hmestone 

 of the valley appears to belong to one great bed, and the granular quartz to be embraced in 

 it, in the form of a great bed also. 



Again, following the mass in the direction of the west branch of Green river, we find a 

 limestone dipping beneath, or plunging into the South mountain, a mountain lying mostly 

 between New-Ashford and Hancock : this, it would seem, must be the same mass which dips 

 beneath Stone hill. Some doubts then may well be excited whether, as has been suggested, 



