99 GEOLOGY OF THE THIRD DISTRICT. 



sition to assume, in parts, the poqihyritic character, presenting crystalline particles, which 

 are globuliform and not angular, manifesting the same law as in gypsum and other minerals, 

 but upon a minute scale. 



Associated with gneiss and granite there are a few other rocks, but they are rare in the 

 third district ; some of them formed by one or more elements of granite or gneiss, with am- 

 phibole or hornblende, forming sienite, granito-sienite and hornblende rock ; likewise some 

 aggregates of which granular carbonate of lime is the base, and others more rare, in which we 

 find pyroxene and table or tabular spar. It is with hornblende rock, granite and gneiss, that 

 magnetic iron ore, the characteristic ore of the range, is usually associated. Another and a 

 common occasional aggregate is that of gneiss and granite with garnet, which was seen in 

 place, in several localities, but is often met in boulders, as well as the hypersthene rock, which 

 was not seen in the district in place, and probably was derived from the second district, where 

 it is an abundant rock. 



The rensselaerite of Dr. Emmons occurs in the district, near to Lewisburg furnace, where 

 the white variety predominates. It is also found to the east of Boonville, some distance from 

 the river, from whence very beautiful specimens have been brought. This mineral, from its 

 great beauty, the high polish which it admits, the facility with which it can be worked, and 

 from being found in considerable quantity, will in great measure supersede many of our com- 

 mon mantel ornaments of stone, as well as other smaller ones. 



The primary rocks cover but a very small area of the district, in comparison with the two 

 eastern ones ; further details, therefore, would seem superflous, as full illustration will be 

 given by the reporters of those districts, especially by Dr. Emmons, being but an appendage 

 to his central mass ; also by the mineralogist of the State : the subject being again introduced 

 in this report, under the heads of those counties where these rocks form a part of the surface. 



The wood cut No. 1, placed at the head of the chapter, is a good illustration of the joints 

 or fractures which this rock usually presents in the district, when it shows a mural surface. 

 It was taken by the side of the Utica railroad, facing the river at the east end of the gap at 

 the uplift of Little-Falls. 



The localities where the primary rock appears insulated from its central mass, showing 

 itself as a protruded body, are but few in number. The first along the Mohawk going east 

 is at the Noses, being found on both sides of the river, at the east end of the uplift, rising on 

 the south side to about one hundred feet ; the greatest height being at some distance from 

 the river. It shows itself in throe distinct patches on that side, and but one on the other, all 

 of different heights, the result of an original uneven surface ; for the whole mass there, from 

 the undisturbed slate of the calciferous and other rocks which rest upon it, must have been 

 raised as one body. 



The next place along the Mohawk is Little-Falls. There the primary rock attains to nearly 

 the same height, at the east end of tlie uplift ; its surface dipping west, and disappearing 

 under the river and its superincumbent masses. The rock exhibits a local character of some 

 interest, which was noticed with detail in the report of Herkimer county. Some of the nume- 

 rous vertical joints on the south side of the river are coated with red oxide of iron, often very 



