QUARTZ CONGLOMERATE. 501 



Fig. 18. If so, probably it was overlaid by the quartz rock. Indeed, we find the quartz 

 in the vicinity of the conglomerate in Plymouth, where, as in Wallingford, it is associated 

 with brown hematite. Yet most of the quartz is wanting in Plymouth, except some beds 

 below the conglomerate. Whether denudation has swept it away (which is most prob- 

 able, judging from the amount of quartz bowlders strewed through the valley) , or whether 

 metamorphism has here converted the sandstone into schist, as is quite possible, we will 

 not attempt to decide. Yet having been led by one class of evidence, chiefly palaeonto- 

 logical, to refer the quartz rock to the Medina sandstone, and by another class to refer the 

 conglomerate to the Oneida conglomerate, their juxtaposition and superposition rather 

 strengthen the presumption that such was their origin. 



It ought to be remarked, that if it be admitted that the principal deposit of quartz 

 rock along the western side of the mountain, may be metamorphosed Medina sandstone, 

 it does not follow that the numerous beds of quartz interstratified with the schists and 

 gneiss in other parts of the State, are of the same age. They may be of different ages 

 in different places, and have experienced different degrees of change. Some of these 

 quartz beds are white as snow ; others are gray, but almost hyaline ; both are often very 

 pure, the ingredients once associated with them having been abstracted, perhaps in the 

 manner we have endeavored to indicate in our remarks upon metamorphism. 



It happens, however, that there is one deposit of quartz rock, of no great thickness, in 

 the southeast corner of the State, in Vernon, whose geological age we can, with some 

 probability, fix upon. To do this, we must follow the rock on the line of strike southwest- 

 erly into Bernardston, in Massachusetts. There we find it dipping at a small angle, and 

 overlying a bed of limestone, which abounds with encrinites. We have already, in our 

 description of clay slate, given the details of this case, and stated Prof. Hall's opinion, 

 that the age of this limestone cannot be older than the Onondaga limestone of the Devo- 

 nian group. The quartz rock lying above it is probably about of the same age. 



According to these views we start with the oldest of the Silurian rocks on the west side 

 of the State, and end with the Devonian on the east side. But it does not follow that 

 there is an uninterrupted succession of newer and newer formations on the way. For we 

 have no doubt, as we have endeavored to show in another place, that the rocks are ar- 

 ranged in several anticlinal and synclinal folds, whose higher parts have been deeply 

 denuded, and thus older strata, we know not how old, have been exposed, so that in 

 crossing the State we may pass over rocks of various ages. Our impression, upon the 

 whole, is, that the several bands of clay slate may mark out layers as high as the upper 

 part of the upper Silurian or even Devonian strata. The band along Connecticut River 

 may indicate the second or third replication. 



We have been led to these suggestions (they hardly deserve the name of regular con- 

 clusions) by the facts that have been detailed. But as they do not accord with any of the 

 various views that have been offered by eminent geologists, we do not expect that they 

 will receive much consideration. We do not offer them with any ambition to propose 

 any new hypothesis respecting these difficult phenomena, nor in the expectation that they 

 afford a complete explanation of the phenomena ; but only in the hope of making a little 

 advance into the region of the doubtful and unknown. Long as we have been in the 

 geological field we have never taken .any decided ground on this subject ; nor, indeed, 



