G. P. Merrill— Ophiolite of Warren Co., N. T. 189 



vesicular glass containing abundant porphyritic olivines ex- 

 ternally altered and sometimes completely changed to iron 

 hydroxide. Small yellow augite crystals are also present. 

 The second of these specimens (No. 3) is a porous black and 

 almost opaque glass including sharp olivine crystals. Lath- 

 shaped forms resembling feldspar microliths also occur here, 

 but they are now wholly l^laced by some isotropic substance. 

 No. 58 is a pumiceous fragment of a reddish gray color. 

 Under the microscope it is seen to be composed of a colorless 

 glass filled with minute yellow augite crystals and iron oxide 

 globulites. In this matrix are abundant olivine crystals, now 

 however almost wholly replaced by iron hydroxide. 



Basalt Tuffs — two specimens from the western end of the 

 island of Fernando are composed of fragments of glassy 

 basalts cemented by zeolites. No. 54 is of a brownish color 

 speckled with white (zeolite) and shows its fragmental charac- 

 ter very distinctly when examined with a lens. The micro- 

 scope discloses angular or rounded fragments of a reddish or 

 yellow glass. These are of various sizes and are very vesicular, 

 containing altered olivine crystals, lath-shaped microliths and 

 opaque octahedrons. In external aspect this specimen resem- 

 bles palagonite but it is not wholly soluble in acids and con- 

 tains too many crystalline components to be properly classed 

 under this head* 



No. 62, collected near the last, is a rock of similar character, 

 but of less pronounced fragmental appearance. It is of a brick- 

 red color, compact in structure and also filled with zeolitic 

 minerals. Under the microscope it is seen to possess a charac- 

 ter quite like the one last described, except that the glass is a 

 deeper red and more opaque. 



Petrographical Laboratory, Johns Hopkins University, Dec, 1888. 



Art. XXI. — On the Ophiolite of Thurman, Warren Co., 

 JV. Y., with remarks on the Eozoon Canadense y by 

 George P. Merrill. 



The Warren County OjDhiolite or Yerdantique Marble as 

 seen in the limited amount put upon the market, consists in its 

 typical development of an even granular admixture of white 

 calcite and pale yellowish green serpentine in about equal pro- 

 portions. The uniformity of texture is, however, often inter- 

 rupted by large irregular blotches of deep lustrous green ser- 

 pentine which, as shown in a large block in the National 



*Renard mentions grains of palagonite in a fragmental rock collected by 

 Buchanan on Rat Island, loc. cit., p. 11. 



