554 The American Naturalist. [June, 
RECENT LITERATURE. 
Lapparent’s Course in Mineralogy,' second edition, is a 
valuable book to any one interested in the more theoretical method of 
discussing crystallography and mineralogy. By far the most interesting 
portions of the volume are those relating to crystallography and physical 
mineralogy. ‘The first part is concerned with a discussion of the gen- 
eral principles of symmetry, and the development of the different crys- 
tallographic systems. The method of treatment is philosophical and 
clear. More emphasis is placed on the general laws governing crys- 
tallization than is usually the case in text-books of this class. The 
clear explanations of the relations of the different systems to each 
other, and of the development of these in accordance with the general 
law of symmetry, are, however, rendered somewhat obscure to the 
non - French reader by the use throughout the volume of the Lévy 
system of crystallographic notation, without the least reference in the 
text to the corresponding Naumann or Miller notation, That portion 
of the book devoted to the physical properties of minerals treats — 1, 
of the general laws governing the propagation of light; 2, those gov- 
erning polarization and interference of light; 3, the mechanical, 
electric and thermal properties of crystals; 4, the grouping of crystals ; 
5, isomorphism and polymorphism; and 6, crystallogenesis. This 
second portion of the treatise is no less philosophical than is the first 
part. Many of the obscure points in physical mineralogy, merely 
touched upon or left unnoticed in most text-books, are treated here 
with as much fulness as could reasonably be expected. The importance 
attached by the author to the subject of mineralogical physics may be 
deduced from the fact that 140 of the 647 pages of the volume are 
occupied in its treatment, while 200 contain the morphological dis- 
cussion, leaving 260 to include the description of mineral species, etc. 
The third portion of the work, that treating of the mineral species, is 
by no means as satisfactory as the first two parts. The description of 
the species are not sufficiently full, nor are the figures of crystals as 
good as they might be. On the other hand, the axial ratio of each 
species has been recalculated, and the results of recent measurements 
have been incorporated in the text. Quite a good deal of space is 
also devoted to the microscopic characters of many of the species, so 
1A. de Lapparent; Cours de Mineralogie, 2d ed. 598 ills. x pl. 647 pp. Paris, 
890. 
