PETROLOGICAL ABSTRACTS AND REVIEWS 709 



consists essentially of albitite, with accessory apatite, zircon, and rutile, and 

 with small amounts of muscovite and quartz. The albitite has the character of 

 the "chequer" albite of Flett. The quartz-albitite is similar to the preceding 

 but contains a blue opalescent quartz. The muscovite-aibitite contains essen- 

 tial muscovite, some of which is regarded as primary, though some is secondary. 

 The amounts of quartz and muscovite are not stated. The first and third rocks 

 belong to 11 12 (new form) of the reviewer's system, the second is 118 if the 

 amount of quartz is over 5 per cent, as it presumably is since these rocks are 

 contrasted with quartz-bearing albitites. 



TiLLEY, C. E. "The Occurrence and Origin of Certain Quartz- 

 Tourmaline Nodules in the Granite of Cape Willoughby," 

 Trans. Roy. Soc. South Australia, XLIII (1919), 156-65, pis. 2. 



Certain nodules, consisting essentially of quartz and tourmaline, occurring 

 in an aplite intrusive in granite, are considered as having developed by the 

 replacement of albite and microcline by tourmaline. Says the writer: " Micro- 

 scopic and other evidence tends to show that they are strictly penumatolytic 

 products. In the slides is to be seen the very act of replacement of feldspar by 

 tourmaline." 



TsuBOi, Seitaro. "On the Determination of the Limiting Values 

 of the Medium Refractive Index of a Finely Crushed Biaxial 

 Crystal by the Immersion Method," Jour. Geol. Soc. Tokyo, 

 XXV (1918), 38-41, fig. I. 

 Maximum and minimum values of refractive indices are readily determin- 

 able but the intermediate value must be obtained from a carefully oriented 

 section or be computed. In the latter case the angle between the t axis and 

 one of the optic binormals must be known. In the present paper is given a 

 method of determining limiting values for /3, based on the fact that it must 

 always lie between the two values observed in a crystal section of any orienta- 

 tion. By making observations on many grains, the difference between upper 

 and lower Umiting values may be made very small. Using basic plagioclase, 

 the author made determinations to 0.003. 



TsuBOi, Seitaro. "Notes on Miharaite," Jour. Geol. Soc. Tokyo, 



XXV (1918), 47-58, pis. 2. 



The term miharaite is given to a lava from the volcano Mihara on the island 

 of Oshima, Idzu. It is a basalt characterized by abundant phenocrysts of 

 bytownite with a few of hypersthene and clino-hypersthene, and a very small 

 amount of augite. The groundmass contains labradorite-bytownite microlites, 



