372 GEOLOGY OF THE SECOND DISTRICT. 



limestone extends ten miles, to or near Tylerville in Rutland, and about twenty in the direction 

 of Adams. A curved line extending from Adams to about two miles north of Tylerville, marks 

 the southern boundary of the irenton, wliich is succeeded by the Utica slate in a very narrow 

 belt, probably not more than two miles wide. This last rock is succeeded by the Lorainc 

 shales, wdiich forms the surface rock of Rodman, Lorainc and Pinckney in Lewis county. 

 The Grey sandstone, upon the extreme borders of Loraine, is but an insignificant mass in this 

 county, though it is largely developed only a icw miles south. 



The shales of Loraine extend west to near Mannsvillc, but do not approach Lake Ontario 

 nearer than eight miles in this county ; they have, therefore, quite a circular border, with 

 the convex edge turned to the north and west. The Utica slate presents the same curved 

 edges, but it barely crops out from beneath the upper rocks. The Trenton limestone, being 

 a firmer rock, in fact more so in this county than in Clinton, extends as far as the Black river, 

 which it approaches in a high bluff about four miles east of Watertown ; from thence it forms 

 the banks of the river to Watertown, where, immediately west of the village, it disappears 

 in consequence of a fracture, and the birdseye becomes the surface rock to Brownville. From 

 Watertown, the line of junction between these rocks runs in the direction of Henderson. 



The lake shore in the west part of Ellisburgh is formed by thick beds of white sand, which 

 conceals the rocks beneath. Whether the trenton limestone which appears near Ellisburgh, 

 dips beneath the sand and lake, or is broken up as in many other parts of the county, is not 

 clear. 



At the present time, it is impossible to determine the former extent of the rocks of this 

 county. We see that though they lie in nearly horizontal positions, still they have suffered 

 from abrasion. We may conceive that each rock, whose general boundaries have been given, 

 may have been extended much farther than we now find them. They all present broken edges 

 at the north, with thick beds remaining, which is not the form they possessed when first 

 deposited. 



Tlic principal feature which results from this arrangement, is, that a series of steps are 

 formed, by which we ascend from the lower to the higher rocks in a regular gradation. The 

 first step is from the potsdam sandstone to the birdseye limestone ; the second from the birds- 

 eye to the trenton limestone, for the mass of black marble beneath the trenton scarcely crops 

 out ; from the trenton we pass to the utica slate, which forms only a narrow platform ; and 

 from the latter, to the loraine shales. 



The middle part of the county is occupied by the birdseye and trenton limestones. The 

 height attained in going up the whole series is probably six hundred feet. This by no means 

 gives the whole thickness of the rock, in consequence of the dip south. 



The above remarks may suffice for a description of the general arrangement of the surface 

 rocks, and of their distribution, together with the peculiar features in the geology which re- 

 sults therefrom. The details in relation to each rock will be more precise and definite, which, 

 together with the preceding, will furnish the reader with the main facts relating to the geology 

 of Jefferson county. 



