44 



APPENDIX TO THOMPSON'S VERMONT. 



UTICA SLATE AND HUDSON RIVER SHALE. 



RED SANDROCK. 



LONE ROCK POINT. 



Charlotte, showing itself in the uplifts, at 

 vai'ious places. It appeal's again in South 

 Hero, and extends northward, through the 

 western part of Grand Isle, and constitutes 

 the south eastern and highest parts of the 

 Isle la Motte. It also caps some of the 

 elevations near the Medicinal Spring, in 

 Highgate. 



This rock is sufficiently compact and firm, 

 in souie places, to serve as a building stone, 

 but it is, for the most part, thin bedded 

 and shaly, and of very little value, except- 

 ing that it forms the basis of a good soil. 



The species of fossils in the Trenton Lime- 

 stone are exceedingly numerous. In the 

 single genus, or this, they amount to no less 

 than seventeen, which are peculiar to this 

 rock ; and in many other genera the species 

 are nearly as numerous. In Grand Isle, 

 this limestone is rather thick bedded, is of 

 a light gray color, and almost entirely 

 made upofshellsof theorthis. This stone, 

 when the edge of the stratified mass was 

 exposed to the heat, was found, unlike 

 most limestone, to withstand the action of 

 the fire, and, on that account, it was much 

 used by the early settlers, for the construc- 

 tion of fire-places, on which account it is 

 still distinguished by the name of fire stone. 



This figure exhibits the gen- 

 KJ.'^i'al form of an Orthis. 



Utica Slate and Hudson River Shales. 

 — Still higher, and to the eastwai'd of the 

 Trenton Limestone, lie a series of black 

 slates. Some of these slates are rather 

 thick bedded, are quite calcareous, and 

 break with conchoidal fracture, and, lying 

 immediately above the Trenton Limestone, 

 are in some caseSj with difficulty, distin- 

 guished from it. In other parts, the slaty 

 laminse are quite regular, and readily sep- 

 arated. But far the greater part of it 

 appears to be crushed and broken into 

 wedge-shaped masses, intei'spersed- with 

 seams of calcareous spai\ In many places, 

 these wedge-shaped shaly masses are cov- 

 ered with glazing, giving them the lustre 

 and appearance of anthi-acite. So strong 

 is this resemblance to coal, that many have 

 supposed that thoi'e must be coal beneath 

 it, and considerable excavations have been 

 made in it with the vain hope of finding it. 



These shales are the only rock in the 

 place, in Alburgh ; they form nearly the 

 whole of North Hero, the eastern half of 

 Grand Isle, Rock Dunder, .Juniper Island, 

 and most cf the other small islands ; and it 

 forms the bank of the lake, along the east 

 side, throughout almost its entire length. 

 With the exception of that portion of them 

 which lies next to the Trenton Limestone, 



these shales are totally useless as a building 

 stone. They, however, disintegrate into a 

 black, rich soil, and are a valuable material 

 for making roads. 



Trilobites are occasion- 

 ally met with, particular- 

 ly in the older portion, 

 which has been sometimes 

 separated from the other 



^ ., ,.^ shales, under the name of 



Tribohte. tt.- on , ,, 



Utica blate, as well as in 



the Isle la Motte Limestone, before descri- 

 bed. 



Graptolites are 

 common in some 

 Graptolites. few places, but as 



a whole, these shales are quite barren of » 

 fossils. The above cut will furnish some 

 idea of the general appearance of grapto- 

 lites. It pretty nearly represents Grapto- 

 lites aviplcxicaule, found in the Trenton 

 Limestone. 



Red Sandrock. — The next series of rocks, 

 lying above and to the eastward of shales, 

 has been generally known in the neighbor- 

 hood, as the Red iSandrock formation. This 

 rock extends from south to north nearly 

 the whole length of Lake Champlain. It 

 makes its appearance in uplifts, presenting 

 mural precipices towards the west, with a 

 dip from 5'^ to 30^ towards the east. Its 

 western limit is marked by a series of con- 

 siderable hills, which are at some little 

 distance from the lake shore at the south 

 and in the northern part of Franklin coun- 

 ty; but from Shelburne to St. Albans Bay, 

 it lies, for the most part, along the shore of 

 the lake. Sugar Loaf and Glebe Hill, in 

 Charlotte, Red Rocks and Lonerock points, 

 in Burlington, and Mallet's Head, in Col- 

 chester, belong to the same line of uplifts. 

 The accompanying cut represents a section 

 passing through the uplift at Lonerock 

 Point, where the thick bedded sandrock is 

 seen resting on black glossy shales. 



The shale, here, has been washed out 

 from under the sandrock, large masses of 

 which have broken off by their weight and 

 fallen into the lake. These, excepting one, 

 are covered, when the lake is high, but 

 that one is seen at all times, and from all 

 points of view, to stand prominently out of 

 the water ; hence the name. Lone-rock 



