422 The American Naturalist. [May, 



Miscellaneous.— New books, etc.— Mr. Lane 1 has recently 

 published two tables for the use of students in optical mineralogy and 

 petrography. One is devoted to the rock forming minerals. These are 

 divided into three classes, the opaque, the isotropic and the anisotropic 

 groups, and the members of "the latter class are subdivided in accord- 

 ance with the strength of their double refraction, their habit and the 

 character of their extinction. There is no doubt but that with a 

 little practice the student may easily learn to distinguish between the 

 various minerals found in rocks if he will only follow the scheme 

 carefully after reading the explanation accompanying it. In the sec- 

 ond table the author gives an excellent resume of Rosenbusch's classi- 

 fication of massive rocks, as elaborated in his ' Massige Gesteine.' An 



even more recent tabulation of igneous rocks is that of Dr. Adams 2 , 

 since it reflects Rosenbusch's present attitude with respect to rock 

 classification. In it the author represents in a very concise and simple 

 form the differences between the various types of massive rocks, and 

 suggests at a glance their relationships. In each of three horizontal 

 columns are placed the plutouic, dyke and volcanic rocks in such a 

 way that the corresponding members of all classes fall in vertical col- 

 umns. The novel features of the classification are the following : Leu- 

 cite-syenite is made a sub-group under the eleolite-syenites, and the 

 tinguaites are represented as their corresponding granitic dyke forms. 

 The rocks in which leucite, nepheline and melilite replace feldspar are 

 given columns between the orthoclase and plagioclase rocks, as better 

 indicating their chemical affinities than is the case when they are 

 placed beyond the plagioclastic rocks. Each of the three groups is 

 divided in accordance with the presence or absence of olivine, and in 

 the niche for the plutonic nepheline combination is placed the new 

 type iolite, recently described by Ramsay". The lamproph} -ric dyke 

 melilite rock is alnoite. Among the lamprophyric plagioclase nephe- 

 line rocks are fourchite and monchiquite, the latter with and the 

 former without olivine. Malchite is a new rock described by Osann. 

 It is the granitic dyke form of diorite. The diabases are put in the 

 paleovolcanic class, which, by the way, is not sharply defined from the 

 neovolcanic class. The basic non-feldspathic rocks are separated into 

 the pyroxenites and the peridotites, which names sufficiently define 

 themselves. Dr. Adams deserves the thanks of all petrographers for 

 l Am. Geol.,June, 1891, p. 341. 

 2 Can. Rec. of Sci., Dec, 1891, p. 463. 

 'Cf. American Naturalist, 1892, p. 334. Bv mistake iolite occurs in * Iie 



