TRAPPEAN DIVISION. 
283 
Origin of Trap Rocks. 
It is now universally conceded, that the trappean rocks shew in themselves, and in the 
effects produced by their protrusion between and through the strata of other rocks, undoubted 
evidences of having been, at the time of their protrusion, in a highly heated state. If the 
question was still open to discussion, the facts that may be seen by a careful exploration of the 
shore of the Hudson between Hoboken and Stony point, where trap dykes have cut througn 
the strata, and overflowed on the top; have changed the sandstones and shales into scoria- 
ceous masses, and other forms that have been detailed ; have formed crystallized minerals in 
the cavities, such as would necessarily be formed by a chemical union of the predominating 
elements of these rocks, as schorl, epidote, etc. ;* the sublimation and crystallization of mi¬ 
caceous oxide of iron, and the sulphuret and oxide and carbonate of copper ;* the interlami¬ 
nation of injected masses between the strata from the dykes, and that have produced the 
same effects in the strata contiguous to them, as have been produced on similar strata adja¬ 
cent to the dykes and to the overflowed masses ; would afford a mass of evidence sufficient 
to convince the mind of those most skeptical on this subject, and demonstrate that the Pali¬ 
sades, and the rest of that range of trappean rocks, are ancient lavas, that have flowed 
through the rocky fissures in dykes, while this part of the continent was still beneath the 
waters of the ocean.f 
The trappean rocks that I have examined in Massachusetts and Connecticut, and that 
have been described by Profs. Hitchcock and Silliman, and that will be described by Mr. 
Percival, the Geologist of Connecticut; those of Nova Scotia, described by Messrs. Alger 
and Jackson ; those of Virginia, Pennsylvania and New-Jersey, described by Profs. Rodgers ; 
and those of Lake Superior, described by Lieut. Allen, Dr. Houghton, &c., offer evidences as 
incontestible, of the same origin. It is probable, but yet to be demonstrated, that the trappean 
rocks of Nova-Scotia, Lake Superior, and east of the Rocky Mountains, and their asso¬ 
ciated red sandstones and subordinate strata, are all of the same geological epoch, and due to 
the same general causes as those of Massachusetts, Connecticut, New-York, New-Jersey, 
Maryland, Virginia and North Carolina. 
Serpentine Rocks. 
These rocks are classed generally with trappean rocks, and are due to the action of the 
same general causes modified in some manner unknown to us. They are different in chemi¬ 
cal composition and external characters. They are usually associated with trappean or horn- 
blendic rocks. Serpentine rocks occupy an extent of several square miles on Staten island, 
between New-Brighton, Tompkinsville and Richmond. The highest point of the Serpentine 
ridge is said to be three hundred and seven feet above tide water. 
* Prof. H. D. Rodgers. Geological Report of New-Jersey, 1840, pp. 150, 154, 155, 157, 161, 162, 164, 165. 
f The evidences on the last point, if considered necessary, are yet to be adduced. 
