PERKNITE {LIME-MAGNESIA ROCKS) 509 



ANALYSES OF PERKNITES ; LIME-MAGNESIA ROCKS. 



4. Pyroxenite. — Johnnycake road, Baltimore. Bull. U. S. 

 Geol. Survey, No. 168, p. 42. Composed entirely of hypersthene 

 and diallage. 



5. Websterite. — From Mt. Diablo. W. H. Melville, analyst. 

 Bull U. S. Geol. Survey, No. 168, p. 213, and Bull. Geol. Soc. 

 Am., Vol. II, p. 406; analysis No. 242. The rock is composed 

 of orthorhombic pyroxene and diallage. 



'Owing to analytical reasons this determination of ferrous iron is unsatis- 

 factory. — W. F. Hillebrand. 



'This determination somewhat doubtful. — W. F. H. 



