Oct. 1906] PROCEEDINGS s. t. ass'n arts and sciences. "^"J 



enclosure, which refers to fragments of foreign rocks merely imbedded 

 within sedimentary, metamorphic, or igneous rocks, or to microscopic 

 enclosures within rocks and minerals. Examples are given of occlu- 

 sions on Manhattan Island and in Westchester County, and the phe- 

 nomena in connection with them are discussed. 



The rock outcrops which we have always called serpentine or soap- 

 stone, in the vicinity of New Rochelle, Hoboken, and on Staten Island, 

 are referred to by the author as "so-called serpentine" and are discussed 

 as occlusions of "serpentinoid," in connection with the associated 

 gneisses, schists, and granites, and its probable influence as an easily 

 eroded rock, in the formation of river valleys, in the vicinity, is sug- 

 gested, especially the valley of the lower part of the Hudson between 

 Manhattan Island and Hoboken. 



In regard to the Staten Island area the author states that the thick- 

 ness has been estimated at "less than 100 feet!" It is unfortunate that 

 the source of information in connection with this statement is not given, 

 as all surface indications, and such facts as are available from the rec- 

 ords of well borings, show a greater thickness ("A One-Hundred-and 

 Fifty-Feet Well in the Soapstone." L. A. Camacho, Proc. Nat. Sci. 

 Assn. S. /., vol. vi, Dec. 11, 1897, p. 45, and a record of 600 feet in a 

 well at New Dorp, given by Lewis Woolman in Ann. Kept. State Geol. 

 N. J., 1899, p. 132, noted in Proc. Nat. Sci. Assn., S. /., vol. vii, Oct. 

 1.3, 1900, p. 46. 



The specific gravity of two specimens from "the point north of Tomp- 

 kinsville" are given as follows: "Dark gray amphibolite, 2.863; li^ht 

 gray tremolite schist, 2.844." 



The author assumes that the main mass of our serpentine rock over- 

 lies the pegmatite granite which outcrops on the shore near the Tomp- 

 kinsville station of the Rapid Transit RR., but says: "Its contact 

 with this later intrusion would not necessarily indicate its lower limit." 



References to the work of several investigators on the microscopic 

 examination of our rock are cited, and the results of personal examina- 

 tions of the Hoboken rock are given. 



The genesis of serpentine rock in general is next discussed, and the 

 theory of its origin by alteration of a sedimentary rock is dismissed with 

 the brief sentence: "There is no longer need of discussion of this view." 

 Almost equally brief are the discussions in relation to its possible de- 

 rivation by direct serpentinization of dolomite and by alteration of 

 amphibolized dolomite,— both of which theories are regarded as not 

 supported by the facts. 



An exhaustive discussion of the chemical and mineralogical charac- 



