406 JULIEN 



the edges of the area, where the massive rocks come in contact 

 with the gneiss.^ 



Serpentinoid Outcrops in the County. — Many beds of so- 

 called "serpentine" are distributed through this region north 

 of Manhattan Island. That at New Rochelle has been found 

 rich in partly altered diopside, enstatite (Dana) or bronzite (F. 

 J. H. Merrill), tremolite, often hydrated (*' hydrous anthophyl- 

 lite ") and actinolite, with a large amount of carbonates, lying 

 mostly in veins and nests of dolomite, magnesite and calcite. 

 Other accessories are marmolite, brucite, deweylite, chromite, 

 magnetite, spinel and perhaps zoisite. 



To the north of Rye an extensive tract of serpentinoid lies 

 near to a ferriferous dolomite. Tremolite, and sometimes 

 actinolite and dolomite, occur in all stages of alteration to 

 hydrated forms, to amorphous serpentine and in part to talc. 

 Pyroxene and chromite have also been recognized (Mather and 

 Dana). 



At Portchester, several beds of serpentinoid occur, and small 

 masses with traces of bronzite near Tarrytown.^ In nearly all 

 these localities this rock has been found with the same associa- 

 tions and alteration-products, particularly steatite, carbonates 

 and limonite, with chert, jasper and chalcedony. 



Serpentinoid Ridge on Opposite Side of Hudson River. — On 

 the west, across the Hudson river, and along the very edge of* 

 its right bank, ridges of so-called '* serpentine," evidently once 

 continuous, stretch for a distance of 14 miles, rising from an 

 elevation of 70 feet at Hoboken, New Jersey, with an area of 

 30 acres, to nearly 420 feet on Staten Island, with an area there 

 of 1 3 i^ square miles. 



At Hoboken the actual outcrop extends about one third 

 mile along the river bank, with a breadth not exceeding 30a 

 feet. In the park south of Stevens Institute a knoll of this 

 serpentinoid was formerly exposed, the most southerly exten« 

 sion of the outcrop, with attached coating of a serpentinoid 

 talus-breccia, the cement of the fragments consisting of brown 



JJ. F. Kemp, idem, (3), XXXVI, 1888, 253. 

 2 Merrill, loc. ciL, 40-41. 



