48 NEW YORK STATE MUSEUM 



George H. Williams published a preliminary account of this rock 

 in March 1887 (9) and in August of the same year he gave (10) 

 the most complete account up to this time. He showed that the 

 rock was not metamorphic in origin but a peridotite dike of igneous 

 origin. In his article he says : " The main points of evidence, 

 therefore, that the serpentine at Syracuse was originally an igneous 

 and intrusive rock, belonging to the family of peridotites, are as 

 follows: (1) the structure of the rock, which is such as is only 

 known to be produced by crystallization from a molten magma ; 

 (2) the existence of a more granular and porphyritic modification, 

 as is so often the case in eruptive dikes; (3) the inclusion in the 

 rock of fragments of the adjacent limestone and possibly of other 

 rocks brought up from below; (4) the indication that these lime- 

 stone fragments have been modified by the action of heat; (5) the 

 fact, stated by Mr Wilkinson, that 50 feet away from the exposure, 

 on the strike of the rocks, only gypsum was encountered." He adds : 

 " This evidence has been developed at such length, because aside 

 from its bearing upon Doctor Hunt's theory of the origin of serpen- 

 tine, this rock is interesting as being the only known instance in the 

 unaltered and undisturbed Paleozoic strata of New York." 



This last statement overlooked the records already published on 

 the Manheim, Ithaca and Ludlowville dikes. 



Williams compares the Syracuse peridotite with that of Elliot 

 county, Kentucky, in which he says : " In structure, the two rocks 

 present the closest possible similarity. The size and form of the 

 large porphyritic olivine crystals appear to be identical in both ; 

 the ground mass of both also has the same appearance, containing 

 in each case an abundance of opaque and transparent octahedral 

 crystals. Nevertheless, certain mineralogical differences are appar- 

 ent. The pyrope with its alteration rim, described by Mr Diller, 

 is wanting in the Syracuse rock ; ilmenite too, estimated to compose 

 2.2 per cent of the Kentucky peridotite, was not detected in the Syra- 

 cuse occurrence. On the other hand, biotite and enstatite are much 

 more important constituents in the latter than in the former. . . 1 . 

 The little transparent crystals in the Kentucky peridotite are con- 

 sidered by Mr Diller as anatase (octahedrite) while those in the 

 Syracuse rock must, however, be regarded as perofskite." 



Following Williams's paper were others by J. F. Kemp (35) and 

 by P. F. Schneider (19), (24), (27), (29); D. D. Luther (21); 

 C. H. Smyth, jr (25) ; and E. H. Kraus (31). 



