49 GEOLOGY OF THE THIRD DISTRICT. 



an inferior stone to the next mass above it in succession, where hard usage is to be encountered ; 

 the latter rock being more rare on the Mohawk, and not so easy to work. 



Black River. The cliff which forms the western margin of this river, consists generally 

 of a limestone in thick layers, tlie upper ones unusually thick. It is the surface mass, 

 and forms a \^rrace, which, were it not for a few water courses which have in places removed 

 it, would extend unbroken through Lewis county. Its mineral character is generally the 

 same witli tlie birdseye, especially the layers below the upper surface one ; being rather brittle, 

 and breaking with a smooth and flat conchoidal surface. 



The cliff shows several distinct kinds of limestone, not being a homogeneous mass. The 

 upper part is intermixed irregularly with black shale, and exhibits the characters and position 

 of the mass intermediate to the birdseye and the Trenton limestone of the Mohawk, which 

 position it also holds. It is not so good a stone as the lower layers, which arc purer, and con- 

 tain the Fucoides dcmissus replaced by white crystalline limestone, which, however, are 

 not so numerous as in the same limestone on the Mohawk, but show identity in other 

 respects. 



The surface of the upper layer contains the remains of large orthocerae, of a structure similar 

 to that of the species duplex, and forming the genus Actinoceras of Bigsby, and Diploceras 

 of Conrad. The edges of the cells, which extend from the internal to the external cone, give 

 to this fossil, when broken or water-worn, the appearance of the backbone of a fish, and it is 

 usually considered as such by the unpractised observer. Some of these orthocera; arc eigh- 

 teen inches or more in length, and from three to four inches in breadth. In the same layer, 

 nejir the mouth of Sugar river, I have found the Strophomena alternata, and the Cyathophyl- 

 lum, which, if it be not the same, resembles the ceratites. The large and handsome cham- 

 bered Columnaria sulcata, the same which is found in the thick layers resting upon the birds- 

 eye at Tripes hill, etc. is often seen in the exposed surface of this rock. The fossils, there- 

 fore, of this part, connect it with the base or immediate under-rock of the trenton, as it 

 exists on the Mohawk. 



Since the commencement of the Black River canal, considerable quantities of stone have 

 been quarried near the mouth of Sugar river. The first layers are the same with those which 

 form the bed of the river, and are not used : they form one division of the mass. The second 

 division is of a lighter color, with less shale or impurities, more brittle, and contains the 

 Fucoides demissus, Orthostoma, etc. : this is the part which is worked. The third division, 

 and which there forms the base of the cliff, does not afford so good a quality of stone as the 

 one above it, but contains the same fucoids ; it is light colored, and the surface of some of 

 the layers present mud cracks, showing the presence of shale. It is in these layers that the 

 stone exists which is burnt for water-lime at Lowville : it is of a yellow color, becoming 

 earthy after long exposure. These three divisions seem to be coextensive with Lewis county, 

 having seen them in many points. 



The cliff rises from the level of the river, a little to the south of the parallel of Boonville, 

 and attains in its passage down the river the height of thirty, and even sixty feet above the 



