Geology and Batural History. 463 



Nomenclature. The system demands a neAV nomenclature and 

 this has been provided for according to a definite system. As 

 proposed it consists of three parts, sul3stantive names for the mag- 

 matic units, impljdng the chemical composition and the 7ior)n / 

 then two sets of adjective terms to qualify these nouns, one 

 referring to the mode and the other to the texture. 



The raagmatic name consists of a root, geographical in all cases 

 except for the names of the five classes, and of a sufiix. The suf- 

 fixes are cjiosen so that they vary in a definite way with the 

 division of the system to which the magmatic name belongs. 

 Thus for Class, Order, Rang and Grad, the letters n, r, s and t in 

 alphabetical order are used with the vowel a, giving in English 

 arte, are, ase, ate. For subclass, suborder, etc., the vowel is o, 

 giving one, ore, ose and ote. 



In the geographical roots, so far as possible those in present 

 use are retained, advantage being taken of their connotation as 

 to magmatic character. 



The authors propose a nomenclature for field use based on 

 purely megascopic characters. 



The work concludes with a discussion of methods of calculat- 

 ing mineral composition from chemical composition and the 

 reverse, and presents tables to aid such calculations. l. v. p. 



4. Petrography and Geology of the Monzoni region in Tyrol. 

 — The exhaustive study of this area, so long known and so much 

 investigated as to be perhaps rightly called a classic one, has 

 recently received a new impetus, apparently from the suggestive 

 work of Brogger (ii Die Eruptionsfolge der triadischen Eruptiv- 

 gesteine bei Predazzo in Stidtirol). A number of shorter articles 

 by various authors have appeared describing new types of rocks 

 or various phases of its geology. Quite recently, however, more 

 important memoirs on the geology and petrography of the region, 

 the one by Romberg (Geologisch — petrographische Studien im 

 Gebiete von Predazzo i and ii, (Sitzber. d. K. preuss. Akad. d. 

 Wiss. Berlin, 1902, phys. mat. class. 675), the other by Doeltek 

 (Tscher. Min. and Petro. Mitt., vol. xxi) have been published. 

 The various authors have not entirely agreed among themselves 

 regarding various points and this has led to a stimulation of in- 

 terest in their work. As a result many new analyses and descrip- 

 tions of important rock types have been given. It is shown that 

 the forecast of Rosenbusch on theoretical grounds, regarding the 

 existence of nephelinitic and other alkaline types, was correct, and 

 in general a considerable amount of new information, of value 

 to systematic petrography, has been developed by these excellent 

 studies. L. V. p. 



5. Gesteiashunde fur Techniker, JBergingenieure etc., von F. 

 RiNNE. (8°, 206 pp., 4 pis., 235 figs. Geb. jknecke.) Hanover, 1901. 

 — In this excellent and well written little volume is given a general 

 survey of the subject of petrology from the modern standpoint, 

 with especial reference to its use by beginners and those desiring 

 some knowledge of th.e subject for technical purposes. It is also 

 a good introduction to the science for w^orkers in other fields in 



Am. Jour. Sci. — Fourth Series, Vol. XIV, No. 84. — December, 1902. 

 32 



