496 AGE OF CLAY SLATE. 



thrown some doubts upon this conclusion, by his reasoning upon the fauna; of the Quebec 

 group. (Amer. Jour. Sci., March, 186] .) His previous opinion was, that the Georgia 

 group was not older than the Hudson River group. The subject is in able hands, and 

 will doubtless require much time and labor to settle it. 



The age of the ranges east of the mountains is settled with even more difficulty, because 

 the metamorphisni is more thorough, and the age of the adjoining rocks is obscure. In 

 order to find any fossils (so far as yet examined) in connection with the slate, we must 

 pass out of Vermont into Canada on the north, and Massachusetts on the south, with the 

 exception of the plant in Guilford, above described. 



On the south we find the clay slate of Guilford extending a few miles into Bernardston, 

 in Massachusetts. Here we find it associated with limestone, quartz rock, and magnetic 

 iron ore ; and the limestone contains encrinites. The position of these rocks may be seen 

 on the section on Fig. 266, which has been already described. 



Commencing at the S.E. we find a small knoll of distinct clay slate, with a strike N.E. 

 and S.W., and a dip of 31 S.E., which are the strike and dip of all the other strata, ex- 

 cepting the obscure and disturbed conglomerate and slaty quartz immediately beneath 

 the limestone whose strike and dip are uncertain. The quartzose conglomerate lying 

 above the limestone is somewhat insulated from the other rocks, but the above is its 

 probable relative position. The quartz rock lying immediately above the bed of lime- 

 stone is very distinctly stratified, with some mica interlaminated, and often jointed. It 

 extends northeasterly, into and through Vernon, but nowhere, save in Bernardston, have 

 we found any slate lying above it. The great body of the slate, as the geological map 

 shows, lies to the west and below the quartz. The semi-crystalline limestone is separated 

 from the quartz by a thin bed of slate, and embraces a bed of magnetic iron, some of 

 which has passed to the condition of limonite, not differing in appearance from bog ore. 

 Only a few rods beyond the limestone northwesterly, we find a rock made up of fragments 

 of quartz and slate, whose position is uncertain ; but a little further is a slaty, dark col- 

 ored quartz, apparently dipping northwest. Beyond this, at no great distance, we conic 

 to the clay slate, with a low dip, and as we proceed northwesterly we reach the great body 

 of the clay slate with a higher dip and a strike upon an average considerably nearer the 

 meridian. A little to the south and east of the limestone and quartz, the oolitic red 

 sandstone, or more probably the new red or permian formation of the Connecticut valley 

 covers the older rock with a westerly dip. 



Now the limestone above described contains at least two species of encrinite, which 

 Prof. James Hall thinks may belong to the period of the Ononclaga limestone of New 

 York, at least that they are not from an older rock. This rock is somewhere near the 

 middle of the Devonian system. Assuming this to be correct and it will bring at least 

 some of the Vermont clay slate into that system. The quantity of slate that lies above 

 the limestone at Bernardston is indeed small, but sufficient to make it certain that at least 

 a portion of this rock has that position, and is therefore not older probably than the De- 

 vonian age. The great mass of the slate does indeed lie below the limestone at Bernards- 

 ton. But if the latter be the Onondaga limestone, there is still thickness enough in the 

 Schoharie sandstone, Cauda galli grit and Oriskany sandstone of New York, to embrace 

 all the Guilford clay slate, before getting as low as the upper Silurian, although it is not 

 easy to see how clay slate could have been formed from these New York rocks. 



