532 PETROLOGICAL ABSTRACTS AND REVIEWS 



Merwin and Larsen. "Mixtures of Amorphous Sulphur and 

 Selenium as Immersion Media for the Determination of High 

 Refractive Indices with the Microscope," Amer. Jour. Sci., 

 XXXIV (191 2), 42-47. 



For minerals having very high refractive indices, Merwin and Larsen 

 propose using molten sulphur, molten selenium, and mixtures of the two, 

 these substances being miscible in all proportions when in a molten 

 condition. The mixtures are prepared by placing the required weight of 

 powdered selenium in a three-inch test tube, heating it until the mineral 

 is thoroughly fused, and allowing it to cool. The proper amount of pure 

 flowers of sulphur is now added and the mixture heated just enough to 

 allow thorough mixing with a glass rod. As the material cools it is 

 gathered on the rod and is cut into small fragments. These may now 

 be returned to the tube, which should be corked, and preserved for use. 



To determine refractive indices with this preparation, a small piece 

 of it and a little of the mineral, finely pulverized, are heated together on 

 an object-glass and under a cover-glass, over a small flame, until the 

 preparation is liquid, when the two are mixed and pressed into a thin 

 film. The film is again heated for half a minute until bubbles begin to 

 appear, when it is again pressed thin and cooled, after which the deter- 

 mination is made in the usual manner. 



A. J. 



Milch, L. "Grundziige der Kristallographie," Taschenbuch f. 

 Math. u. Phys., Leipzig u. Berlin, 1913, 359-81. 



Milch, L., and Renz, Carl, "Ueber griechische Quarzkera- 

 tophyre," Neues Jahrb., XXXI (191 1), 496-534. 

 In Argolis and on Hydra, quartz keratophyres and keratophyre tuffs 

 appear, probably of Devonian age. Seven analyses are given. 



A. J. 



Milch, L. "Ueber die Beziehungen des Riesengebirgsgranits, 



(Granitit) zu dem ihn im Siiden begleitenden Granitzuge," 



Centralhl. f. Mm., etc., 1911, 197-205. 



In an earlier paper Milch had asserted that the two granite areas in 



question form a single intrusion, the two-mica granite being simply 



an altered phase of the granitite. Rimann maintained that the two 



areas represented distinct intrusions. The present paper is a reply to 



Rimann, and reasons are given for the contention that the mass is a unit. 



A.J. 



