364 RANGE AND EXTENT. 



York in the town of Sandgate, is the largest, and is the most useful of all in an economi- 

 cal aspect ; for a great part of it is checkered with numerous quarries of roofing slate. 



Passing north from Sandgate into Rupert and Pawlet, the band of clay slate gradually 

 widens, and attains its maximum width in Poultney and Fairhaven. Thence northerly 

 it gradually narrows till it terminates in Cornwall, near the east village. 



In Pawlet, Wells and Poultney, there is very little of special interest attached to this 

 rock. It crops out very frequently, showing itself in beautifully rounded bosses of bright 

 colored slates. It is not generally of such a texture that it can be used for economical 

 purposes ; and near its eastern limits it assumes somewhat of a talcoid character. As 

 the clay slate and talcoid schists meet they are interstratified with each other. The pas- 

 sage from one formation to the other is not abrupt. 



One who wishes to see the best development of the Georgia slate in Vermont, should 

 examine the numerous slate quarries in Castleton and Fairhaven. So many excavations 

 have been made, and so much material thrown out, that all the lithological characters of 

 the rock, and the different textures and colors of the useful slates are profusely exhibited. 

 Many of the quarries illustrate beautifully the difference between the planes of cleavage 

 and of true bedding. The details of the position and characters of the Georgia slate in 

 these two towns are fully stated in the description of Section VI. 



There seem to have been several local elevations of the slates of this terrain. We 

 know not how extensive these may be ; whether sufficiently so as to modify our views of 

 the thickness of the strata we know not. We noticed at the Eagle Slate Company's 

 quarry in Castleton an elevation of a few feet, so that the same strata are repeated upon a 

 small hill east of the quarry. 



Prof. Adams, in his Third Report upon the Geology of Vermont, says that the line of ponds which extends 

 from the south part of Sudbury through Wells was found to occupy the place of a long fracture and uplift 

 of the slate formation, the mural face of which fronting to the west is found on the eastern margin of the 

 ponds and with scarcely an interruption for the whole distance. It is worthy of notice that notwithstand- 

 ing the magnitude of this fracture and uplift, no other formation is thrown up to view. 



There is a peculiar concretionary slaty rock belonging to this group of rocks along the 

 west shore of Lake Bombazine. Between Section VI. and the northern termination of 

 the deposit in Cornwall, the same general characters are presented as upon the district 

 already described. Section VII. crosses the deposit in Sudbury, where the slate is quite 

 narrow, forming a mountain ridge. The most northern ledge seen is in the north part of 

 Cornwall. It is there interstratified with the Eolian limestone ; not resting upon the 

 limestone as some have supposed, judging chiefly from theoretical veiws. It may, 

 however, rest in an inverted synclinal axis, and thus the sudden thinning out of the slate 

 be more plausibly explained. 



But one of the most singular associations of this rock would seem to throw doubt upon 

 the usual theory of the separation of the slate from the limestone. One would imagine 

 that the slates were a formation entirely distinct from the limestones, and that the 

 limestones form a group by themselves. We think it is extremely difficult to draw the 

 line between the Georgia slate and the Eolian limestone which runs down the west side of 

 the northern extremity of the Georgia slate. As one travels from Fairhaven through 



