RANGE AND EXTENT. 365 



Hubbardton, Benson, Orwell and Sudbury, along the limits of the two rocks, he will be 

 perplexed by the numerous alternations of clay slate and limestone. The limestones are 

 very insignificant in Fairhaven, but they gradually increase in amount northward until in 

 Orwell and Sudbury the slate is insignificant in amount. The phenomena might be 

 explained by the theory that the two kinds of rock are interstratified normally, but that 

 in the north'partof the terrain the slates have gradually dwindled till they have nearly disap- 

 peared, and that the reverse is the case in proceeding southerly, namely, the slates 

 predominate at the expense of the limestone. We do not venture to adopt this theory, 

 but simply state it as a view which occurred to us in the field as one that would solve 

 many difficulties. Section VII. enumerates carefully all the different beds of slate and 

 limestone in its path. It grves the proportions of the two rocks more carefully than Sec- 

 tion VI. in Castleton and Fairhaven. There ought to be two other careful sections 

 measured across these rocks to the north part of Hubbardton, and the north part of Castle- 

 ton. Perhaps several points of agreement would be found in all four of the sections when 

 they are compared together. 



The second deposit which we have doubtfully referred to the Georgia slate, is colored 

 upon the map as clay slate simply. It is a narrow strip upon the west side of the talcose 

 conglomerates, separating them from the Eolian limestone between Westford and Starks- 

 boro'. We are almost disposed to associate with it, and thus add to its length, certain 

 talcoid rocks associated with the quartz rock further south. Perhaps they were originally 

 the same rock, but are now changed by metamorphism. If so, then its first appearance 

 beginning at the southern termination is found upon Section VII, in the northeast 

 corner of Brandon, in Forestdale. The rock here is probably argillo-talcose schist (Nos. 

 xso) i0i an d roa i n the Cabinet.) An allied rock, holding the same geological position, 

 occurs upon Section VIII at Ripton (Nos. J^, ^ and ^ in the Cabinet.) 



In the extreme east part of Bristol, at the Furnace, a similar rock, but decidedly talcoid 

 in its appearance, is found, lying east of pure vitrified quartz rock, and west of a conglom- 

 erate. The next locality where it was noticed is in the north part of Starksboro, east of 

 Mr. Hill's house (formerly occupied by James Chase), east of the quartz rock. Its extent 

 is not known. We saw a similar rock next in the valley of Lewis Creek, in the southeast 

 part of Hinesburgh, where it is properly four miles wide, although only the west edge of 

 it is colored as clay slate upon the map. The rock, however, seems to be nearly a talcose 

 schist. Section X. crosses it two miles further north. Passing into St. George the band 

 of rock curves westwardly, and the clay slate now forms a conspicuous part of the deposit. 

 The slate curves back again to the east, north of St. George, in Williston. The slate has 

 two colors here, the western part is black, and the eastern part is green. Southeast of 

 the village of Williston, over a distance of two miles, the green character of the slate is 

 very evident. The belt is wider at this point than it is at any other locality either north 

 or south of Williston. 



Between Williston Center and Winooski River the vast deposits of alluvium have con- 

 cealed the rocks from view. But at Hubbell's Falls, near Essex Junction, the clay slate 

 is conspicuously displayed in the bed of Winooski River. It is calcareous, and its junc- 

 tion with the Eolian is distinctly seen, though the junction itself is perplexing. The 

 ledges of black clay slate between the Falls and Essex Center are exceedingly numerous 



