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NEW YORK STATE MUSEUM 



quartz, tourmaline, plilogopite, and magnetite can be readily recog- 

 nized, while in the slides, scapolite is abundant and small masses of 

 titanite are everywhere through the somewhat altered plilogopite. 

 Pyrite and apatite also appear. It is an unusually complex bunch 

 of silicates in the limestone series. The dark schistose rocks that 

 penetrate the limestones in instances apparently parallel to the 

 foliation are shown by the thin sections to consist of brown horn- 

 blende, rather scarce brown biotite, plagioclase, some pyroxene and 

 magnetite. Either hornblende or augite may fail. The rocks are 

 at times quite gneissic or even massive, as in the great sheet just 

 over the limestone of the abandoned Pease Quarry in the outskirts 

 of Port Henry. In thin sections these more massive sheets bear 

 the strongest resemblance to the metamorposed dikes from the Hud- 

 son Piver shore above TVest Point, described by the writer in the 

 American Naturalist for August 1SSS. There is much that leads 

 one to regard them as intruded dikes and sheets, doubtless contem- 

 porary with the gabbro, and offshoots from its magma, that have 

 afterwards become foliated by metamorphism. Such a dike from 

 the limestone quarry near the Pilfershire Mine is shown in the 

 accompanying reproduction of a photograph. It is clearly a broken 

 dike, between whose separated fragments the limestone has been 

 forced. The mineralogy and structure of this is precisely like the 

 gneissic ones above referred to, but less certainty is felt that the 

 more schistose ones may not be metamorphosed sediments. Very 

 similar beds occur in the limestones of Gouverneur, St Lawrence 

 co. where they are regarded by C. H. Smyth, jr as altered sedi- 

 ments, (Trans. K Y. Acad. Sci. XII p. 102 Feb. 23, 1893) and 

 where they are far west of any exposure of gabbro. Their notice- 

 able parallel arrangement in the limestone makes it seem extra- 

 ordinary that dikes should have been so regular unless the apparent 

 bedding of schists and limestones is due to mountain making pro- 

 cesses. One or two beds of light grey gneiss with graphite and silli- 

 manite were met with in the limestone series. One occurs along 

 the highway south of the Pilfershire mine, on the general map. 

 It may represent a silicious bed, deposited in with the limestones. 



Petrography of the gabbros and anorthosites. In the high 

 knobs of Mount Harris, in the western portion of Moriah, near 

 Ensign Pond, and also in the northern part of Westport, the 



