Trans. N. Y. Ac. Set. 58 Dec. 12,. 



able proof should be found of this, if it is true. At present no positive 

 assertions could be made, and the duty devolves on the geological 

 members of the Academy to rid the subject of doubt. 



The fossils in the boulder referred to by Mr. Britton prove to have 

 come from the Schoharie Grit. In its original condition this was a 

 hard, compact blue limestone, but is here presented in a leached state, 

 by the passage of waters containing carbonic acid, with a loss of its 

 lime, color, and density. It was derived from northern New Jersey, to 

 which locality a belt of this rock runs down from Schoharie county. 

 Its transit by ice was effected without doubt through the valley of the 

 Hackensack, which lies east of the Orange Mountains and west of the 

 Palisades. This glacial movement is indicated by the direction of the 

 stricB observed by Mr. Britton, as well as of those in the Hackensack 

 valley. 



Mr. A. A. JULIEN recalled the results of his lithological examination 

 of the serpentines both of Staten Island and of Hoboken, presented be- 

 fore the Academy two years ago, in which it was shown that sections of 

 all these rocks abounded in minute fragments of more or less altered 

 amphibole. The conclusion then stated, that these serpentines must 

 be certainly derived from hornblende schist, was confirmed by the in- 

 teresting discovery of the latter rock, both in well-boring and on 

 Brighton Point. Serpentines of the same general character and origin- 

 occur frequently throughout New York and Westchester counties.. 

 The mineral serpentine is also found in small quantity as a vein-deposit, 

 not pseudomorphous, like the main mass, but presenting an amorphous 

 material with banded vein-structure, associated with magnesite, dolo- 

 mite, etc.; e. g., the marmolite of Staten Island, a translucent green 

 variety found at Hoboken, and also at West 60th street on New York 

 Island, etc. At all these localities the amphibole survives in a more or 

 less altered condition ; e. g., the tremolitic talc schists and slaty tremo- 

 litic serpentines of Staten Island and Hoboken, the hydrous antho- 

 phyllyte and unaltered tremolyte rock of West 60th street. New York, 

 the tremolitic amphibolyte of New Rochelle and Rye, in Westchester 

 county, etc. 



Mr, Britton confirmed the last remarks, by the statement that a 

 stratum of material, strongly resembling the hydrous anthophyllyte of 

 New York, had been struck at the bottom of one of the wells on Staten 

 Island ; also that veins of mixed serpentine and calcite were observed 

 at Stapleton, possessing a banded structure parallel to their walls. At 

 that point the apparent thickness of the serpentine bed is 150 feet, but 

 the crest of the hill is composed of talcose schist. 



Mr. W. Le Conte Stevens then read a paper on "The Mam- 

 moth Cave of Kentucky." 



