383 GEOLOGY OF THE SECOND DISTRICT. 



arc absent, tliey uniformly belonij to tlie upper part. Such are the facts in regard to this rock 

 in the northern district, where it is probably as fully developed as in the Mohawk valley, or 

 in any other localities in this country. 



BiRDSEYE Limestone. 



. This rock forms a broad irregular belt through the whole county, from east to west. Its 

 whole breadth is at least ten miles. Its northern outcrop, upon an east and west line, passes 

 through Depauville, and a point two miles south of Evans' mills on the great bend of Indian 

 river ; from this point, it runs to the great bend on the Black river, and from thence to a point 

 two miles southwest of Carthage. Its disappearance at the south, under the trenton lime- 

 stone, is along a line extending from Champion nearly direct to Watertown. In this outline, 

 I do not pretend to follow its windings ; for on its outcrop, it will be perceived that in conse- 

 quence of its having been exposed by denudation, it must necessarily present an indented 

 rather than a straight edge to the north ; and so on the south also, in consequence of the break- 

 ing up and wearing down of the trenton by which it is brought into view, the same irregular 

 exposure will necessarily be the result. 



The birdseye of Jefferson may be ranked among the thick-bedded rocks, some of the strata 

 being at least two feet thick. Between the thick beds there are a few inches of shaly matter, 

 in which we find a few fossils ; but in general it is a compact rock, breaking with a con- 

 choidal fracture, and weathering to an ash color. In this county, it is sufficient to remark, 

 that it exhibits its usual characters, or those which have been given in the general account of 

 the rocks of the Second district. 



Along the Black river, the birdseye limestone appears to contain a greater number of fossils 

 than elsewhere. Commonly the fossil called the Fucoides demissus, is the only one it contains ; 

 but here I have observed several, particularly a very large species of orthoceratite, often mea- 

 suring eight inches in diameter at the base or largest part. Some are still larger, having 

 a diameter of twelve inches, and a length of ten feet. In the upper part of the rock at the 

 great bend on the Black river, the Cytherina is common, together with a species of the Caly- 

 mene and Strophomena. But the remarkable compactness of the rock, and its shght wea- 

 thering, make it almost impossible to procure perfect specimens even of parts of any fossil. 



In addition to the large species of orthoceratite, I found one less than the ordinary size, 

 which, from its frequent occurrence here and at a few localities in the Mohawk valley, must 

 be considered as characteristic of this rock. It is the Orthoceratites multicameratus (Fig. 93). 



