338 Prof. Beck on Igneous Action, as exhibited in New York. 



two or three hundred yards near Port Richmond, and which 

 again appears at Bergen, New Jersey, and onward forms the 

 Palisadoes of the Hudson. The connexion between this range 

 and the serpentine is too obvious to need farther notice. 



Serpentine has been found on the island of New York, but not 

 in large masses. On the peninsula east of New Rochelle in 

 Westchester County, it is abundant, and has the appearance of a 

 distinct dyke. Its structure is somewhat columnar, and it is 

 every where traversed by seams of softer magnesian minerals, 

 asbestus, &c. On the west, it is said to be bounded by horn- 

 blende rocks, while on the east is a limestone more or less mixed 

 with serpentine. 



Similar in their characters, are several deposits of serpentine in 

 the counties of Dutchess and Putnam. At Brown's quarry in the 

 latter county, this columnar or basaltic appearance is well exhib- 

 ited. The serpentine is here very dark colored, and varies in its 

 structure from compact to coarse crystalline, like some hornblendic 

 rocks; to which, indeed, in hand specimens, it not unfrequently 

 bears a close resemblance. The fissures contain crystals of horn- 

 blende, plates of Schiller spar, and dark colored tremolite. 



There is a fine illustration of the intimate connexion between 

 trap and serpentine, although upon a small scale, on Stony Point 

 in the county of Rockland. Trap dykes pass up the northwestern 

 face of this hill, which are well marked in consequence of the 

 decomposition of the hornblende rock. Now these dykes are 

 every where traversed by a soft greenish substance belonging to 

 the serpentine family. They contain also asbestus in very deli- 

 cate silky fibres. 



In Lewis County, near Natural Bridge, where trap dykes and 

 trappean aggregates are not unfrequent, there are mural precipices 

 made up chiefly of the substance called Rensselaerite by Dr. 

 Emmons, but which I suppose to be a mixture of steatite or ser- 

 pentine with pyroxene. The same mineral occurs in unbroken 

 ledges in the vicinity of Ox Bow, Jefferson County, a region in 

 which well characterized trap dykes are common. 



So also in St. Lawrence and Essex counties, whenever serpen- 

 tine is found in any abundance, dykes of trappean rocks are to be 

 seen in the immediate vicinity. 



We have strong grounds, therefore, for adopting the theory of 

 the igneous origin of serpentine, were we furnished only with the 



