July 9, 1909] 



SCIENCE 



59 



drawings are not up to the usual standard, 

 especially that set by Gennan writers. 



In the discussion of the elements of min- 

 eralogy a brief review of the essentials of 

 crystallography is undertaken. It would seem 

 that altogether too much space is given over 

 to the calculation and projection of crystals 

 and not enough emphasis placed upon a mas- 

 tei-y of their general morphology. For after 

 all, the petrographer is far more concerned 

 about the general features of crystal form, as 

 revealed in the thin section, than he is about 

 the calculation to the fourth decimal place of 

 the elements of crystallization. 



In the chapter on the application of polar- 

 ized light to crystalline substances the optical 

 behavior and methods of determination of 

 crystals are treated. In too many cases are 

 the phenomena, to be observed, described with- 

 out any attempt being made to explain them. 

 This is especially the case with the discussion 

 of the formation of uniaxial interference 

 figures. The statement on page 46, " The 

 student must keep in mind the principles of 

 polarization of light as given in Chapter II.," 

 needs to be corrected, as polarization is not at 

 all referred to in the chapter indicated. 



Parts two and three are the most important 

 features of the text. The descriptions of the 

 various minerals are in all cases full and in- 

 clude, aside from a discussion of the crystallo- 

 graphic, optical and other physical properties, 

 paragraphs treating inclusions, recurrence, 

 diagnostics and classification. Many figures 

 showing the optical orientation accompany 

 these descriptions. The discussion of the feld- 

 spar group is very exhaustive, covering forty- 

 seven pages and including fifty-four figures. 

 The analytical tables are well arranged and 

 usually lead to a rapid and accurate deter- 

 mination of the mineral under consideration. 



Although the authors have failed to present 

 the principles and methods of optical mineral- 

 ogy in a manner which will allow of a ready 

 comprehension by the beginner, they have 

 nevertheless succeeded in making easily ae- 

 ce.ssible the more important data of rock- 

 forming minerals. This feature alone is suffi- 

 cient to commend the book to the use of 



advanced students of petrography and physical 

 crystallography. Edward H. Ejsaus 



mixeralogical laboratory, 



University of Michiqan 



Gold: Its Geological Occurrence and Geo- 

 graphical Distrihuiion. By J. Malcolm 

 Maclaren, D.Sc. Cloth, 6 X 10 ins., pp. 

 687. London, The Mining Journal. 

 Maclaren's " Gold " is a recent acquisition 

 to a somewhat overworked field of endeavor. 

 The work has been compiled, as such works 

 must needs be, through much painstaking 

 effort extending over a number of years; an 

 important consideration being that a large 

 part of the information presented has been 

 verified by investigations made by the writer 

 which add weight and authority to the state- 

 ments. 



The book is divided into two parts, namely, 

 the General Relations of Auriferous Deposits 

 and the Geographic Distribution of Gold. In 

 the first part is a general discussion of the 

 occurrence of gold, including a general state- 

 ment regarding the structure of the earth and 

 its relation to ore deposits. There is a brief 

 discussion concerning the zone of fracture, 

 sources of metallic ores and xinderground 

 waters, filling of fissures, secondary enrich- 

 ment, etc., but it is doubtful whether they 

 should not have been discussed at greater 

 length or not considered at all. 



There is an interesting section devoted to a 

 discussion of the physical and chemical char- 

 acters of gold, its alloys and natural com- 

 pounds. 



The geological occurrence of auriferous de- 

 posits is taken up under the head of Classifi- 

 cation of Deposits, which is divided into two 

 groups, the primary and secondary, the occur- 

 rence by countries, districts, etc., being con- 

 sidered under these heads. It is needless to 

 say that an attempt to cover the occurrence of 

 gold throughout the world in seventy odd 

 pages is much too big a task to be done com- 

 prehensively. 



The bulk of the book is devoted to a dis- 

 cussion of the geographical distribution of 

 gold, and while fairly exhaustive leaves much 



