1885.| Mineralogy and Petrography. 393 
and their relation to the symmetry of the crystal, has just pub- 
lished a short text-book of mineralogy,’ which, however, is very 
elementary in its character, being intended only for use in high 
schools or for the self-instruction of beginners. 
Dr. Aristides Brezina, of the University of Vienna, has pub- 
lished the first part of an elaborate and exhaustive series of crys- 
tallographic researches, undertaken in competition for a prize 
offered by the Royal Academy of Science? The first part, 
although covering over 350 octavo pages, deals only with meth- 
ods of investigation, and constitutes a most valuable addition to 
the works on mathematical crystallography. 
Fr. Ulrich, of Hanover, is the author of a quarto pamphlet, 
containing sixteen pages, covered with figures to illustrate the 
relations of the crystalline forms of the different systems, the de- 
velopment of hemihedral forms and some characteristic combina- 
tions of common minerals3 Many of the figures are colored. 
and, while roughly executed, they are useful in making plain to 
beginners some of the more elementary principles of crystallog- 
raphy.. No printed explanations are appended. : 
A much-needed elementary text-book of microscopical miner- 
alogy has very recently appeared, by Dr. Eugen Hussak, o 
Gratz.‘ Only such species are treated as enter into the composi- 
tion of rocks, and these almost exclusively in reference to their 
appearance and the methods of their identification in thin sections 
under the microscope. The first part of the book deals with the 
methads of microscopical petrography—the construction of the 
microscope and the manner in which the optical properties of 
minerals are used for their identification ; the method of sepa- 
rating rock constituents by means of a heavy solution, micro- 
chemical analysis and some of the most peculiar characteristics 
common to all minerals when examined in thin sections. The 
second part contains the distinguishing microscopic peculiarities 
of each rock-forming species arranged in tables, as is the case in 
Professor Brush’s manual of Determinative Mineralogy. These 
are sometimes too concise to be satisfactory, but they nevertheless 
contain a great amount of information in a very small space. The 
means of distinguishing similar minerals are especially empha- 
sized. A valuable list of references to the more important micro- 
scopic studies of different rock-forming minerals, arranged alpha- 
betically, is annexed to these tables. The book is not a text-book 
of petrography, since.rocks themselves are not described, but 
1 Kurzes Lehrbuch der Mineralogie einschliesslich der Petrographie. Von H. 
Baumhauer. 8vo, pp. 190. Freiburg, 1884. 
* Krystallographische Untersuchungen an homologen und isomeren Reihen. Von 
$ 3 i 8 o. pp- 9. 
Dr. A. Brezina. 3 Theil, Methoden, Wien, 1884. 2 abe 35 hen Vorlesungen 
Von F. Ulrich. Hanover, 1885. : : 
í Anleitung zum Bestimmen de gesteinbildenden Mineralien. Von Dr. E. Hus- 
sak. Leipzig, 1885, pp. 196. 
