412 Scientific Intelligence. 



8. Elements of Optical Mineralogy ; by N. H. and A. N. 

 Winchell. 8°, 502 pp., many figs, and col. plates. New York, 

 1909 (Yan Nostrand Co.). — The authors state in the preface that 

 this work had its inception under the impulse of a conviction that 

 English students and independent workers in petrography needed 

 a clear and systematic description of the apparatus used and the 

 methods employed in this science. They feel that the principles, 

 methods and data of optical mineralogy have not yet been pre- 

 sented concisely and clearly in any single publication and it is 

 their aim to supply this deficiency. 



In accordance with this view the first chapter is devoted to an 

 explanation of the nature of light and such of its phenomena as 

 are of importance in this connection ; the second deals with the 

 elements of crystallography ; the third describes the general 

 phenomena of optical mineralogy and the apparatus used in inves- 

 tigating them from the petrographic standpoint. These three 

 chapters contain 100 pages, and of necessity, since they cover so 

 wide a field, the material is greatly condensed. It is illustrated, 

 however, by man}^ figures which serve to explain the text. 



The remaining portion of the volume is devoted to a descrip- 

 tion of all minerals which are important as rock constituents, or 

 which are sufficiently transparent to have optical properties, 

 especial emphasis in all cases being laid upon the latter in the 

 description. Numerous figures in the text help to convey the 

 optical characters in succinct form. 



Whether the teacher or student of petrography decides to use 

 this, or one of the several other excellent works we now have, as 

 his main reliance in gaining a mastery of the principles of this 

 subject, he will at all events find this volume a most serviceable 

 handbook of reference with respect to the optical properties of 

 minerals. As such it will prove a great convenience in the 

 library of every working mineralogist and petrographer. 



l. v. P. 



9. Geology of the Taylorsville Region, California; by J. S. 

 Diller. United /States Geological Survey. Bulletin 353. Pp. 

 121, with 5 plates and 12 figures. Washington, 1908. — Little has 

 been published regarding the district in California between 

 Honey Lake and Lassen Peak, a region which has much of geo- 

 logical interest. Dr. Diller's report shows that the " sedimentary 

 rocks of the Taylorsville region contain a more nearly complete 

 record of the geological history of the Sierra Nevada than has 

 yet been recorded in any portion of the range." Eighteen sedi- 

 mentary formations are represented : Silurian 1, Devonian 1, 

 Carboniferous 4, Triassic 2, Jurassic 7, Tertiary 1, and Quater- 

 nary 2 ; the Carboniferous, Jurassic, and Triassic being the rich- 

 est in fossil remains. In place of the single fault bounding the 

 Sierra Nevada farther south, there are in this district at least 

 three more or less parallel fault zones. The easternmost one, — 

 the Honey Lake, — presents an escarpment 2,000 feet high, com- 

 posed of quartz diorite overlain by auriferous gravel and breccia. 



