J«S9-] Mineralogy and Petrography. 443 
of monoclinic and triclinic minerals are constructed, in the 
manner familiar to the readers of the " Mineralogie Microgra- 
phique." The development of the laws of double refraction 
and pleochroism, etc., follow, and the facts thus developed are 
graphically illustrated by diagrams. A special feature of this 
portion of the book is a large, lithographic plate, by means of 
which the nature of the substance composing a crystalline 
particle of known thickness may be determined by noticing 
its color between crossed nicols. The general portion of the 
book concludes with an excellent chapter on microchemical 
reactions. 
In the special portion, (by Lacroix), the chemical, morpho- 
logical, and physical properties of a large number of minerals 
are given in concentrated forms. The appearance which these 
minerals present in the thin section, and their general charac- 
teristics, however, are not described, so that the book is in 
reality a text-book in optical mineralogy. The features which 
have made Professor Rosenbusch's " Mikroskopische Physio- 
graphic " so invaluable as a guide to the detective minerals in 
rocks are lacking in the volume before us, but many of those 
in which the latter is wanting are found in the former in good 
quality. " Les Mineraux des Roches " is really a complement 
to Rosenbusch's work, supplementing it in those very portions 
where the " Mikroskopische Physiographie " is weak. It is un- 
necessary to remark that the book of Levy and Lacroix is one 
to be placed in the hands of a beginner in the study of optical 
mineralogy, although it will prove of inestimable value to him 
who is already familiar with the general principles of the 
science.— Mr. Eyerman' has collected in a pamphlet of fifty- 
four pages descriptions and notices of the new minerals and 
new mineral occurrences that have been discovered in Penn- 
sylvania during the fourteen years since the appearance of Dr. 
Genth's " Preliminary Report on the Mineralogy of Pennsyl- 
vania." The analyses of Pennsylvania minerals that have 
been published during this period are reproduced, and a few 
original observations of new occurrences are given. Authori- 
ties are quoted in all cases, so that the pamphlet is of great 
value to anyone interested in the minerals of Pennsylvania.— 
The " Catalogue of a Collection of Precious and Ornamental 
Stones of North America, Exhibited at the Paris Exposition 
1889, by Tiffany and Co.,," contains a very complete list of 
^ "The Mineralogy of Pennsylvania." Part i., Eastern Pa. 
' New York. The De Vinne Press. 32 pi-. 
