38 GEOLOGY OF THE THIRD DISTRICT. 



tlie upper one of a dark color, with stains of yellow, and the others of a sandy color. A spe- 

 inen of the Ophilela complanata was found here. 



At Henry Deny's, in Clair's patent, the same layers again appear. At the Fish-house, to the 

 east of the village, the rock is exposed in many places ; likewise in Broadalbin, at the Eagle 

 mills, and the creek between there and the Fish-house ; in several streams from thence to- 

 wards West-Galway, and at Hageman's mill in Amsterdam, etc. 



3. BLACK RIVER LIMESTONE. 



Stmonimes. — Birdsejre limestone, Mohawk limestone, Ba«e of the Trenton limestone, as ased in the reports of the third dis- 

 trict. Black marble of Isle la Motte, " Seven-foot tier," and Chazy limestone of Dr. Emmons, the latter mass connecting 

 the biidsrye with the calcifeious sandrock proper. Metalliferous limerock, or Transition limetock of Eaton. 



(No. 2. Pennsylvania Survey.) 



This term is applied to the first range or cliff of limestone on Black river, extending by the 

 side of the river, from opposite Boonville, through Lewis into Jefferson county ; the cliff being 

 composed of the birdseye of the Mohawk, and the rock upon which the well-characterized- 

 Trenton limestone, in many of its locaUtics is placed. It forms a convenient natural arrange- 

 ment from association, from some common mineral characters, thickness, and as regards eco- 

 nomical geology, the two rocks being much used as a building material. 



At Fort-Plain, and other places upon the Mohawk, the change from the Birdseye to the 

 Trenton limestone is perfectly abrupt, the two masses being in contact, one resting upon the 

 other. The surface of the upper layer of the birdseye, at its point of connection with the su- 

 perior rock, is thickly covered in many parts with the fossils of the Trenton limestone, which 

 adhere to it, and not one of which is to be found below the surface of the birdseye ; and recipro- 

 cally, those of the birdseye end with it. The only change visible in the latter rock, is a slight 

 one in its mineral character towards the surface where the Trenton limestone rests upon it ; 

 the smooth fracture and the brittleness which characterize the rock giving place to the more 

 scaly, granular and tougher nature of mass which, in some other localities, is placed between 

 the birdseye and the well-characterized Trenton rock. This abrupt change from the one 

 rock to the other at Fort-Plain, shows that a part is wanting to connect the two, and that part 

 is found in some of the upper layers in the first range of cliffs on Black river, in tlic upper 

 and lower quarry at Tripes hill, in the quarry to the southeast of Amsterdam, in Sage & 

 Reed's quarry, on the south side of the Mohawk opposite Tripes hill, and in a few other 

 places to be mentioned. 



The name Black river limestone is substituted for the Mohawk limestone of the Report of 

 1840. In attempting to correct Mr. Conrad, I was led into a greater error, losing sight of the 



