756 REVIEWS 
Whatever may be our view of the position taken by Professor 
Rosenbusch upon certain mooted questions in petrology, we must 
acknowledge the great value of this recent work, and congratulate the 
author upon its publication. J2Rigs 
A Text Book of Mineralogy with an extended treatise on Crystallog- 
raphy and Physical Mineralogy, by E.S. Dana, New York, 
John Wiley & Sons, 1898. 
This is a new edition of Professor Dana’s former text-book entirely 
rewritten and enlarged. It consists of four parts devoted to crystal- 
lography, physical mineralogy, chemical mineralogy, and descriptive 
mineralogy, and contains an appendix treating of the drawing of crys- 
tal figures, and of projections, besides one giving tables to be used in 
the determination of minerals. 
The relation of crystal form to other physical properties and to the 
probable molecular structure of crystals is set forth in the introductory 
paragraphs of Part I, and the grouping of the crystal forms is made 
in relation to the thirty-two classes of symmetry. For this reason it 
would seem that a morelogical arrangement of the subject would place 
the physical mineralogy first and the crystallography afterwards. 
The arrangement of the types of crystal forms although referred to 
the classes of symmetry is the order usually employed in elementary 
treatises, namely, the group with the most complex symmetry first. 
The necessity for this order of arrangement is questionable. 
The treatment of the six crystallographic systems is quite full and 
in addition to the description of the symmetry and principal forms 
are given their spherical projection and the mathematical relations of 
each system. Compound or twin crystals and the irregularities of 
crystals are described at length and are profusely illustrated. 
The physical characters of minerals are treated briefly in connec- 
tion with those of cohesion, elasticity, and relative density, as well as 
those related to heat, electricity, and magnetism. ‘The optical proper- 
ties are considered at greater length, both as to the principles involved 
and their application to the optical investigation of minerals. In 
this respect the improvement over former editions of the Text Book is 
marked. The part devoted to chemical mineralogy includes a state- 
ment of the general principles of chemistry which apply to minerals 
