OCCLUSION OF IGNEOUS ROCK 



417 



silicates, in part serpentine.^ While the prevalence of this proc- 

 ess in other regions has been established — Massachusetts, the 

 Adirondacks, Canada, etc. — its insufficiency to account for the 

 phenomena at and near Manhattan Island has been already 

 discussed." 



Fourth, Alteration of ultra-basic igneous rocks. 



The application of this hypothesis to the serpentinoid calls 

 for consideration of its chemical and mineralogical character- 

 istics. 



Chemical Composition of tJic Serpentinoid. — We are indebted 

 to Newland for publication of two analyses of these rocks, and 

 a i^\N others are added below for comparison. 



A. *' Light green serpentine," Castle Point, Hoboken, N. J. 

 G. A. Goodell. 



B. ** Dark green serpentine," Castleton Corners, Staten 

 Island, N. Y. Sp. gr. 2.55. G. A. Goodell. 



C. " Serpentine," Kallerangen, Germany. G. Schulze. 



D. " Reddish serpentine," Lower Predannack, Cornwall, 

 Eng. Sp. gr. 2. J J. M. W. Travers. 



E. '* Wehrlite-serpentine," Ladkije, North Syria. L. Finckh. 



F. " Lherzolite- and pyroxenite-serpentine," Sarikaja Mtns., 

 North Syria. L. Finckh. 



SiOj... 

 AljOa. 



FcOg. 

 Feb.. 

 MgO. 

 CaO.. 



A. 



B. 



C. 



D. 



E. i 



36.90 



36.72 



40.77 



40.29 



37-07 



1.29 



1.06 



3.21 



5.10 



1.70 



•45 



.49 



2.81 



— 



— 



, 5-79 



6.59 



1.79 



4.94 



8.03 



1.46 



1-53 



6.12 



3.98 



— 



23-75 



29.09 



21.24 



25.67 



38.12 



15.53 



9-95 



13.74 



11.85 



— 



13-14 



98.31 



14-54 

 99-97 



10.70 



8.17 

 100,00 



14.84 

 99-76 1 



100.38 



39-95 



2.87 



11-55 



32.05 

 13.40 



99.82 



A comparison of the figures in A and B with those of the 

 published analyses of true serpentines from other regions will 

 serve to establish the wide divergence of Goodell's results and 



1 J. D. Dana, Am. Jour. Set., (3), XX, 1880, 32 ; N. L. Britton, Afn. A\ V. 

 Acad. Sci., II, 1881, 167, and Nat. Hist. Soc, Staten Island, 1886. 



2 Julian, loc. cit., 449-453. 



