126 GEOLOGY OF THE SECOND DISTRICT 



places, it is remarkably traversed by seams and veins of calcareous spar and quartz. This 

 is not, however, peculiar to this limestone, and hence those veins do not characterize it with 

 sufficient precision ; and I may remark here, that it is necessary to look carefully to its super- 

 position, in order to satisfy ourselves of the true nature of the mass, or in other words, whe- 

 ther it is a transition or a primary limestone. 



The brief description of this limestone has been given, for the purpose of furnishing a full 

 and complete view of all the Tocks which are embraced in the Champlain group. It does not 

 occur in the Second District in place, but ranges entirely through the valley of the lake which 

 gives name to the group ; but is confined wholly to the Vermont side. In Jefferson county, 

 where the upper portion of this group is tolerably well developed, this limestone is not to be 

 found ; nor is it recognized in the Mohawk valley. 



Thickness. — The whole thickness of the sandstone and limestone is not over one hundred 

 feet, estimating it at those places where the least disturbance exists. Of the thickness of the 

 whole group, it is not possible to arrive at certain conclusions ; but forming our estimate from 

 the individual masses composing it, at those places where the least disturbance exists, or 

 where the beds are nearly horizontal, it is not far from fifteen hundred feet. Going into the 

 disturbed districts, however, those for instance east of the Hudson river, there is apparently 

 an enormous thickness of the shales and sandstones composing the upper part of this group 

 only. If we consider the mass between the Hudson and Massachusetts line as a succession 

 of di,flferent strata, they must form together a thickness of twelve or fifteen miles. Such a 

 view, however, I believe to be incorrect and unwarrantable ; and the probability is, that there 

 is a succession of uplifts, so that there is a frequent recurrence of the same strata, instead of 

 an uninterrupted succession of different beds. This view of the subject is not only favored 

 by the number of long and nearly parallel valleys, but by the frequent appearance of a hard 

 sandstone, which seems to be the equivalent of the grey sandstone and limestone already 

 described, and which without question are the superior rocks of this group. 



