578 PETROLOGICAL ABSTRACTS AND REVIEWS 



orthoclase, may occur, apparently in consequence of the heat liberated by 

 the crystallization of the hornblende. (4) Crystallization of sphene, some- 

 times simultaneous with, sometimes previous to, the hornblende, and in 

 some cases even somewhat later, and at times around previously separated 

 and partially resorbed quartz, orthoclase, and plagioclase nuclei. (5) Crys- 

 tallization of biotite, with occasional resorption of hornblende — probably in 

 consequence of, or at least aided by, the heat liberated by the crystallization 

 of the biotite, with the subsequent separation of more quartz; but inde- 

 pendently of this, quartz, orthoclase, and plagioclase may also appear in 

 connection with biotite for the same reason that they appear in connection 

 with the hornblende, viz., from solution in the originally liquid biotite. 

 (6) Crystallization of plagioclase with occasional resorption of some of the 

 biotite, with subsequent liberation of magnetite. (7) Crystallization in 

 supersilicated magmas of part of the quartz, often as micropegmatite of 

 the a type along with plagioclase, and later, in like manner, with orthoclase 

 also. (8) Crystallization of orthoclase, with solution, in part, of the plagio- 

 clases, apparently from heat of crystallization of the orthoclase with sub- 

 sequent development of micropegmatite of h type in the areas of solution. 

 (9) Solution also, in part, of the earlier orthoclases during the crystallization 

 of the later orthoclases, also with development of micropegmatite of h type 

 in the areas attacked. (10) Crystallization of remaining portion of quartz 

 with little or no action on the previously crystallized minerals. (11) Crystal- 

 lization of microcline if present, with partial solution of plagioclases and 

 orthoclases — the latter in limited degree — with subsequent development 

 of micropegmatite of h type in the areas of solution. (12) Crystallization 

 of remaining liquid magma, if any, with varying conditions, occasionally 

 as micropegmatite of the c type, occasionally as microgranite. 



Albert Johannsen 



NiKiTiN, W. "Drehbarer Compensator fiir Mikroskop," Zeit. 

 Kryst., XL VII (1910), 378-79. Fig. i. 

 Describes a sensitive instrument for measuring weak double refraction. 



W. T. SCHALLER 



NiKiTiN, W. " Halbspharoid zur graphischen Losung bei Anwendung 

 der Universalmethode," Zeit. Kryst., XL VII (1910), 379-81. 



Fig. I. , 

 An apparatus to replace the stereographic net. Used in connection 

 with a Fedorow Universaltisch, the optical constants may be directly 

 drawn, with a pencil, upon the unglazed porcelain surface of the half sphere. 



W. T. SCHALLER 



