PETROLOGICAL ABSTRACTS AND REVIEWS 87 
LEIss, C., and SCHNEIDERHOHN, H. Apparate und Arbeitsmethoden 
sur mikroskopischen Untersuchung kristallisierter Korper. 
Handbuch der mikroskopischen Technik, Part X, pp. 94, 
figs. 115. 
A manual giving in simple form the more important apparatus and 
methods for the microscopical determination of crystals. The authors 
say in the preface that the book is intended only for the use of amateurs, 
teachers, and collectors of minerals who wish to make use of the polar- 
izing microscope. It is, however, a book that can be read with profit 
by the average student of petrology. The authors not only deal with 
the polarizing microscope, but describe the preparation of thin sections, 
the use of the axial angle apparatus, refractometer, etc. The theoretica] 
discussion is simply presented and good, and embraces all the essentials. 
Meap, W. J. “Occurrence and Origin of the Bauxite Deposits of 
Arkansas,” Econ. Geol., X (1915), 28-54, pls. 5, figs. 7. 
The writer believes that the bauxite of Arkansas is derived from the 
weathering of the underlying syenite, and gives analyses showing the 
transition. Previous writers maintained that the deposits were chemical 
sediments or due to the action of hot springs from the still heated syenite. 
MENNELL, F. P. A Manual of Petrology. Chapman and Hall, 
iLondon,;1913) Pp) iv--256, figs. 122. 
This little book is an enlargement of Mennell’s Introduction to Petrol- 
ogy, which was published in tg09. The book has been practically 
rewritten, new cuts have been added, and the form has been considerably 
changed. Fifteen pages are devoted to the general properties of minerals, 
tr to optical methods of determination, 53 to the rock-forming minerals, 
38 to general petrology, 56 to the igneous rocks, 12 to the sediments, 32 
to metamorphism, 7 to weathering, 10 to the distribution of the chemical 
elements, 9 to radio-activity, and 7 to the collection and preparation of 
material. 
Merwin, H. E. “Measurement of the Extraordinary Refractive 
Index of a Uniaxial Crystal by Observations in Convergent 
Light on a Plate Normal to the Optic Axis,” Jour. Washington 
Acad. Sci., IV (1914), 530-34. 
