DIP AND STRIKE. 



275 



Providence Island, 



South Hero, McBride's Bay, 



South Hero, near do., 



South Hero, Sawyer's Bay, 



Sister's Islands, 



Point au Roche, N. Y., 



Point au Roche, N. Y., 



Isle La Motte, south point, 



Isle La Motte, Fisk's, 



Isle La Motte, Fisk's, 



Isle La Motte, southeast part, 



Isle La Motte, hills south of quarry, 



Isle La Motte, do., 



Isle La Motte, north of do., 



N. 22 E., 



N.42E., 



About N. and S., 

 N.40E., 



N.65E., 

 N. 65 E., 



Isle La Motte, hills north of quarry (Black R. limestone), 

 Isle La Motte, do., N. and S., 



40 X., 



4-5 E., 



6E., 



5E., 



6E., 



12 SE., 



12 NE., 



5 NE., 



5 NE., 



5-6 E., 



30 SE., 



5NE., 



4-5 NW., 



45 NW., 



5NE., 



5 E. and 5 W., 



C. B. A. 



C. H. H. 



C. B. A. 



C. B. A. 



C. B. A. and C. H. H. 



C. H. H. 



C. H. H. 



C. H. H. 



C. H. H. 



C. B. A. 



C. H. H. - 



C. H. H. 



C. B. A. 



C. H. H. 



C. H. H. 



C. B. A. 



FIG. 173. 



Chazy L- 



A 



Fio. 174. 



Utica slate. 



B 



Junction ofChazy Lime- 

 stone &. Utica Slate. 



Junction of Chazy Limestone and Ulica Slate. 



The general position of the Chazy limestone is that of a formation dipping at a small angle to the north- 

 east and north. Numerous local exceptions to this rule are found. There is also an anticlinal, that may be 

 traced from Crown Point in New York, across the lake to Chimney Point, thence north- 

 easterly, through the towns of Addison, Panton and Ferrisburgh, into Charlotte. No 

 more is seen of this rock except in the islands in the northern part of Lake Champlain, 

 where the anticlinal is not observable, unless it be at Hill's south quarry in Isle La Motte. 

 Here, there is a small anticlinal in the middle of the quarry. About midway between 

 the docks at each of Hill's quarries on Isle La Motte, there is an irregularity in the dip, 

 and when we examine the ledge we see that two different rocks have been brought into 

 proximity by some disturbance. Fig. 173 represents the position of the slate and the 

 limestone upon the borders of the lake. A, A, indicates the fault between the two. The 

 position of the strata is represented in Fig. 174; from which it would appear that the 

 Utica slate was depressed below the Trenton lime- 

 stone, so as to be at the same level as the Chazy 

 limestone. It is possible that the disturbance has 

 destroyed the original marks of stratification in the 

 slate, and that now, as in the upper part of the lake, 

 the strata seams are obliterated. The area of the 

 slate is about four square rods, and the smoothed side of the Chazy limestone may be traced several rods 

 further with the direction of N. 20E. 



Two other facts indicate that this elevation extended along the whole of the east side of the island. 

 About one-fourth of a mile north of Hill's black marble quarry, a similar conjunction of slate and limestone 

 is seen, of about the same extent. The depression of the slate is less, because the limestone contiguous is 

 Trenton limestone. Were we to regard the slate in its proper place, at the latter locality, it would give a 

 thickness of only 25 feet to the Trenton, which we know to be certainly 200 feet thick on this island. 

 Moreover the Trenton dips west, and the Utica slate dips east, at the junction of the two. As the lime- 

 stone resists decomposition better than the slates, it is probable that the Utica slate of Alburgh and North 

 Hero once filled up the lake between Isle La Motte and those points of land respectively. The depth of 

 the lake east and west of Isle La Motte confirms this view : for it is very shallow upon the east side, 

 and unusually deep upon the west side of the island. The depression, however, must have been much 

 greater at the southern than at the northern extremity of the island. 



The other fact showing disturbance upon this island, is seen at the southeast part. There the strata 

 are all thrown about in various direction, like a gigantic breccia, and the rock is indurated and occasionally 

 rendered crystalline and remarkably ferruginous. Clowk Island shows all these phenomena in perfection. 

 This is a mass of coarse limestone, with very little soil, as we should judge in sailing past it. The west 



