DESCRIPTIONS OF THE FORMATIONS. 19 



In the State of New York the lower part of the Trenton is called the Birclseye. 

 It is a perfectly pure limestone, and the next layer, which is the middle or Black 

 River sub-division, is sometimes used as a marble. It is solid, hard and easily 

 worked, by reason of its conchoidal fracture, and is valuable for lime and for 

 building. 



The upper part of the formation, or Trenton limestone proper in New York, 

 consists of two distinct varieties, at Trenton Falls. The first or upper part, is a 

 dark or black colored, fine grained limestone, in thin layers, separated regularly 

 by black shale or slate, forming the great mass in which the creek has worn its 

 channel, and in which are all the falls. See Note 62, New York. 



The second, or lower part of the Trenton proper, is a gray, coarse grained 

 limestone, in thick layers, and it is quite crystalline. This is the quarry-stone at 

 Prospect, above Trenton Falls. At Montreal, the church of Notre Dame and many 

 other structures, are constructed of the gray variety of the Trenton limestone, 

 quarried behind the city, but the thinner layers, when not dressed, are of a more 

 pleasing color, and make a handsomer building-stone. 



The Trenton formation in all parts of the United States, is almost always a 

 limestone. A conspicuous example of the Trenton, Utica and Hudson River 

 formations, is seen in the long continuous and beautiful valley of the Hudson and 

 Lake Chatnplain, the Kittatinny valley of New Jersey, the Cumberland valley of 

 Pennsylvania, the Shenandoah valley of Virginia, and the valley of East Tennes- 

 see. The fertility of its limestone land is almost inexhaustible. The deposits of 

 brown hematite iron-ore, found in the soil, and occupying hollows or basins in the 

 softer limestones below the Trenton in so many places, and in such large quan- 

 tities, are supposed by some to be of aqueous origin, and not strictly a product 

 of this formation, which is only its receptacle. But many other geologists, R. 

 M. S. Jackson, A. A. Henderson, Lesley, Platt, Prime and Frazer, have all agreed 

 in advocating the opposite view, each from his own independent studies. They 

 derive the lirnonite beds either from the solution of the ferriferous limestone lay- 

 ers, or from the intercalated micaceous slates, or from the pyrites-bearing slates 

 of the neighborhood. According to Dr. Hunt, it comes from the change of masses 

 of iron-pyrites and of carbonate of iron, originally imbedded in the limestones 

 and slates. See the foot note on page 21. 



4 b, Utica Slate, The Trenton limestone is succeeded by a dark or black 

 carbonaceous slate, called the Utica slate. In Pennsylvania this formation is 

 everywhere darkly colored, and the coloring matter is probably derived from 

 abundant remains of marine plants or animals. While the black color of some 

 of the clays in the brown hematite ore banks of the upper range (immediately 

 beneath the Utica slate) as at the mines in Lehigh Co., Pa. , and the Brandon ore 

 mine in Vermont, seems to be derived from the black slates of the Utica, the 

 gray color of some of the limestones, and of the carbonate ores, (as at the 

 Saucon zinc mines) is known to be due to disseminated graphite. 



Within the State of New York, it is everywhere black, and usually soft and 

 fissile. Thin beds of impure limestone are associated with it in many places, and 

 sometimes thin layers of carbonate of iron, and it passes into the Trenton limestone 

 by gradual interstratification. Thus bands of slate are interstratified in the 

 limestone, and thin strata of limestone containing fossil remains in the lower part 

 of the slate. These crumbling shales may generally be distinguished by their 

 dark blue-black and brownish-black color, but there are some strata among the 



