GEOLOGY OF THE CONNECTICUT VALLEY DISTRICT. 455 



bility that the crinoidal Hmestone occupies a small valley in the quartzite, 

 and therefore would be newer rather than older. In other words, it may 

 be the newest rock in this Helderberg section, resting upon the quartzite, 

 instead of underlying it, as is commonly represented. Whether it may 

 not crop out somewhere between the quartzite and Coos slates, remains 

 to be seen. There is nothing in its relations, if correctly interpreted, 

 rendering this an impossible position. The quartzite and slate in the 

 field north stand vertically and dip west. Though the limestone at the 

 quarry seems clearly to dip under the quartzite, we must not forget that 

 the state of things is entirely different close by. That this limestone 

 should bear the structure of an inverted synclinal may seem strange, but 

 it is not any more singular than many similar exposures of Chazy lime- 

 stone in the Champlain valley, as shown conclusively by the presence of 

 fossils. Lesley's views seem to confirm this opinion. 



This view agrees with the interpretation given heretofore regarding 

 the related rocks in the Ammonoosuc area. There the quartzite under- 

 lies the limestone in many exposures. In that region the staurolite slates 

 nowhere touch the Helderberg. In fact, a conglomerate associated with 

 the crinoidal layers contains fragments of a rock supposed to have been 

 derived from the development of Coos schists not very far away, but 

 separated by a well-marked Huronian ridge. There is nothing in the 

 relations of the same two rocks in Bernardston to prevent us from inter- 

 preting them in the same way, /. ^., to regard the slates as much older 

 than the limestone. 



10. Granting that the staurolite slates of Bernardston are the southern 

 end of the Coos group, it does not follow that the latter are of Helderberg 

 age, as Prof. Dana supposes ; for we have first to prove that the former 

 are so intimately associated with the limestone as to be necessarily of 

 the same age. These slates nowhere touch the limestone, so far as 

 known. They are separated by the quartzite. 



1 1. Nevertheless, the Coos rocks are the newest in the whole Connecti- 

 cut valley north of Massachusetts, unless it be this fossiliferous limestone. 

 Provided some intimate connection can be made out between them, — and 

 there is plenty of ground to work over in search of the paleontological 

 evidence, — they may all be regarded as Helderberg. There is nothing 

 incongruous between a Helderberg Coos series and the doctrines laid 



