534 PROCEEDINGS OF NEW YORK MEETING. 



its way in places between them : and, as Been in the exposure on Green street, con- 

 rably disturbing them in its immediate vicinity. Two section?, drawn with care 

 to b lai . Bbow the serpentine in a position in the limestone difficult, if n < > t 



impossible, to account for except "n the hypothesis of eruptive < >i i<_ci n. 



*_'. Inclusions brought <>/> by the intrusive rock from below. — Much of the serpentine 

 i- full of angular fragments of other rocks imbedded in it. Souk; poli.-hed specimens 

 hibited to the S< have al least one-third of their surface composed of auch 

 included fragments. The vast majority of these are composed of the adjacent lime- 

 stone, but others also occur. One specimen contains a large fragment of Mack shale 

 (probably (Jtica shale), which here is over 1,000 feet below tbe surface ; another speci- 

 men remains a fragment of an acid crystalline rock, granite or gneiss, which must 

 here lie over i'.iiiki i ". • < - 1 below the surface. Vanuxem mentions such granitic and 

 syenitic inclusions as not uncommon. They could not, however, have 1 ne im- 

 bedded in the serpentine except at a considerable depth, whence they were carried 

 upward by the molten rock. 



3. 77.. onal alteration of angular limestone inclusions. — As has been already 

 mentioned and as is well shown by the specimens exhibited, the Syracuse serpentine 

 is frequently full of limestone fragments, which differ much in shape and size. All 

 of these included fragments show the effects of contact metamorphism through the 

 influence of heat, and the new minerals which are produced in this way have invari- 

 ably a /.onal arrangement parallel to the 6ides of the fragments. This i- a proof that 

 the metamorphism could only have been effected after the limestone had been broken 

 into its present shape and imbedded in the serpentine; hence the enclosing rock 

 must have been the agent of metamorphism. 



In speaking of the eruptive origin of the Syracuse serpentine it is not, of course, 

 intended to imply that the original eruptive rock was itself serpentine. Serpentine, 

 as i- well known, is always an alteration producl of Boine otber rook — generally of a 

 feldspar, free basic eruptive, or peridotite. The Syracuse rock is not now by any 

 means all Berpentine, although a greater portion of it has been changed by hydration 



into this mineral. Nevertheless, enough of tbe minerals and structure of tl riginal 



rock -till remain to identify it with the particular type of peridotite known a- kim- 

 berlite. 



There is another occurrence of serpentine, with mica crystals one-third of an inch 

 broad, mentioned by Vanuxem at a fault between the Calciferous and [Jtica, near 

 Maiilieim bridge, on East Canada creek, New York. It is associated with crystalline 

 carl onate of lime containing pyrite and blende 



The President, Professor .1 .\ m es Ball: There is a dike of trap rock, also mentioned 

 by Vanuxem, cutting the Genes lates near Ludlowville, New York.f 



\l .1 I' Ki.\ir: There are a number of such occurrences near [ibaca. There are 

 Btnall crack- in tbe Devonian -hale that very Btrongly resemble dike-. In these the 

 material seems to be -hale, ,md i- in such an advanced stage of alteration that it 

 readily effervesces with acid-. The rock i- at least extraordinary, containing as it 

 does abundant biotiie. It has a high specific gravity. The largest dike i- not more 



than two or three inches wide' where it cut- the -hale. 



.i Reports, Vol. I ll. 1842, p. 807. 

 i Ibid., i 



