Reviews — SJiort Notices, chiefly Mineralogical. 83 



study he has been closely associated with Professors F. Becke and 

 F. Berwerth, of Vienna. The present volume gives a general 

 discussion of the subject, based on physico-chemical principles. 

 A second volume is reserved for the description of the crystalline 

 schists of special areas. 



Commencing with a brief historical review and concluding with 

 references to the literature, the subject-matter is divided under four 

 main headings, as follows : — 



A. The original material and its specific characters. 



B. Metamorphism. 



C. The products of metamorphism in their various forms. 



D. The geological occurrence of crystalline schists. 



VII. — The Orbicular Gabbro at Dehbsa, San Diego Co., 

 California. By Andrew C Lawson (Bull. Dept. Geol. Univ., 

 California, vol. iii, 1904, pp. 383-396.) 



A DESCRIPTION is given of the petrographical characters 

 and field relations of an interesting type of gabbro from 

 California. The normal type is a coarse-grained hornblende-gabbro 

 with olivine and hyperstbene, of which there are various local 

 facies, one being the orbicular type. The spheroids, which were 

 mistaken by the original finder of the rock for fossil corals, measure 

 about six centimetres across. They consist of a core of felspar 

 surrounded by concentric shells of radially crystallised olivine and 

 basic felspar, the composition of the whole being that of a troctolite. 

 Some suggestions are offered to explain the orbicular structure of 

 igneous rocks, which though of somewhat rare occurrence is more 

 common in acid than in basic rocks. 



VIII. — Year-Book of the Scientific and Learned Societies of 

 Great Britain and Ireland, etc. 21st Annual Issue. 8vo. 

 (London : C. Griffin & Co., 1904.) 



IT is obvious that a book of reference of this nature, after appearing 

 for twenty-one consecutive years, has filled a want. The Year- 

 Book is thoroughly appreciated by some secretaries, as shown by the 

 up-to-date information supplied. There are still others, however, 

 who lag behind. Why, for instance, has the Secretary of the 

 Geological Society of Glasgow not vouchsafed any details for two 

 years? We also note that Mr. Monckton is still put down as 

 President of the Geologists' Association of London, though succeeded 

 by Dr. A. S. Woodward last February. 



Messrs. Griffin & Co. would add a piece of useful information to 

 each of the smaller local societies if they could obtain from the 

 secretaries the last date on which a publication appeared. " Nothing 

 since 1900 " would be greatly appreciated by librarians, from whom 

 such information is frequently sought. 



