130 



POPULAR SCIENCE MONTHLY. 



oJs and apparatus used in studying the 

 l)hysical characters of crystals, and to 

 record and explain the observed phenom- 

 ena without complex mathematical dis- 

 cussions. The first part of the book re- 

 lates to the geometrical characteristics 

 of crystals, or the relations and deter- 

 mination of their forms, including the 

 spherical projection, the thirty- two 

 classes of forms, the measurement of 

 crystal angles, and crystal projection or 

 drawing. The optical characters and 

 their determination are the subject of 

 the second part. In the third part the 

 thermal, magnetic, and electrical char- 

 acters and the characters dependent 

 upon electricity (elastic and permanent 

 deformations) are treated of. A sug- 

 gested outline of a course in physical 

 crystallography is added, which includes 

 preliminary experiments with the sys- 

 tematic examination of the crystals of 

 any substance, and corresponds with the 

 graduate course in physical crystallog- 

 raphy given in Columbia University. 

 'J'he book is intended to be useful to oi'- 

 ganic chemists, geologists, mineralogists, 

 and others interested in the study of 

 crystals. The treatment is necessarily 

 technical. 



A book describing the Practical MetJi- 

 ods of identifying Minerals in Rock Sec- 

 tions irith the Microscope * has been pre- 

 pared by Mr. L. McI. Luquer to ease the 

 path of the student inexperienced in op- 

 tical mineralogy by putting before him 

 only those facts which are absolutely 

 necessary for the proper recognition and 

 identification of the minerals in thin sec- 

 tions. The microscopic and optical char- 

 acters of the minerals are recorded in the 

 order in which they would be observed 

 with a petrographical microscope; when 

 the sections are opaque, attention is 

 called to the fact, and the characters are 

 recorded as seen with incident light. 

 The order of Roscnbuseh, which is based 

 on the symmetry of the crystalline form, 

 is followed, with a few exceptions made 

 for convenience. In an introductory 

 chapter a practical elementary knowl- 

 edge of optics as applied to optical min- 



* Minerals In Rock Sections ; tho Practical 

 Method of identifying Minerals in Rock Sections 

 with the Microscope. Especially arranged for 

 Students in Scientific Schools. By Lea Mcllvaine 

 Luqner. New York: D. Van Nostrand Company. 

 Pp. 117. 



eralogy is attempted to be given, with- 

 out going into an elaborate discussion of 

 the subject. The petrographical micro- 

 scope is described in detail. The appli- 

 cation of it to the investigation of min- 

 eral characteristics is set forth in gen- 

 eral and as to particular minerals. The 

 preparation of sections and practical op- 

 erations are described, and an optical 

 scheme is appended, with the minerals 

 grouped according to their common op- 

 tical characters. 



Mr. Herbert C. Whitaker's Elements 

 of Trigonometry * is conci.se and of very 

 convenient size for use. The introduc- 

 tion and the first five of the seven chap- 

 ters have been prepared for the use of 

 beginners. The other two chapters con- 

 cern the properties of triangles and 

 spherical triangles; an appendix pre- 

 sents the theory of logarithms; and a 

 second appendix, treating of goniometry, 

 complex quantities, and complex func- 

 tions, has been added for students in- 

 tending to take up work in higher de- 

 partments of mathematics. For assist- 

 ing a clearer understanding of the sev- 

 eral processes, the author has sought to 

 associate closely with every equation 

 a definite meaning with reference to a 

 diagram. Other characteristics of the 

 book are the practical applications to 

 mechanics, surveying, and other every- 

 day problems ; its many references to as- 

 tronomical problems, and the constant 

 use of geometry as a starting point and 

 standard. 



A model in suggestions for elemen- 

 tary teaching is olTered in Califoi'nia 

 I'lunts in their Ho)nes,'<f by Alice Mcrritt 

 Dfiridson, formerly of the State Normal 

 School, California. The book consists of 

 two parts, a botanical reader for children 

 and a supplement for the u.se of teachers, 

 both divisions being also published in 

 separate volumes. It is well illustrated, 

 provided with an index and an outline 

 of lessons adapted to difl'erent grades. 

 The treatment of each theme is fre.sh, 

 and the grouping novel, as is indicated 

 by the chapter headings: Some Plants 

 that lead Easy Lives, Plants that know 



• Elements of Trigonometry, with Tables. By 

 Herbert C. Whitaker. Philadelphia : Eldredge & 

 Brother. Pp. 200. 



+ California Plants in their Ilomes. By Alice 

 Merritt DaTidson. Los Angeles, Cal. : B. R. Bauni- 

 gardt & Co. Pp. 215-133. 



