Reviews — Professor H. Ries — Economic Geology. 181 



is present as felspar. The values for quartz are very much closer 

 and in five cases are in satisfactory agreement". 



The " Summary " also contains appendices dealing with (1) a deep 

 coring for coal near Little Missenden, Bucks, and (2) a Catalogue of 

 Types and Figured Specimens of British Cretaceous Gasteropoda 

 preserved in the Museum of Practical Geology. 



VII. — Economic Geology. By Heinrich Bies, A.M., Ph.D., Professor 

 of Geology at Cornell University. Pourth edition, thoroughly 

 revised and enlarged, pp. xx + 856, 6" by 9", with 291 figures 

 and 75 plates. New York, John AViley & Sons ; London, 

 Chapman & Hall, Ltd. 1916. $4*00 net" 



T 



established book, written especially for American teachers and 

 students, on Economic Geology. Like the previous editions it gives 

 concise descriptions of the composition, mode of occurrence and origin 

 of the economically valuable rocks and minerals of the United States, 

 to which have now been added descriptions of the more important 

 Canadian deposits, and brief references to those of other countries. 

 The latest available statistics of production have been included and 

 each section is accompanied by a valuable bibliography, dealing 

 especially with North American occurrences. The book has been 

 brought up-to-date, and is well illustrated by sections, maps, and 

 photographs. 



VIII. — Origin of the Zinc and Lead Deposits of the Joplin 

 Begion. By C. E. Sienbenthal. Bulletin 606 United States 

 Geological Survey. Washington, Government Printing Office, 

 1915. pp. 283, with 9 plates and 16 figures in the text. 



Ij^OB some dozen years the author was engaged in studying the 

 _ famous zinc and lead deposits of the Joplin region. Besides 

 their great economic importance these deposits have long been of 

 intense interest to students of ore deposition, because they form 

 a conspicuous example of the occurrence of sulphide ores in a region 

 where apparently no plutonic or volcanic activities can have 

 played a part in their genesis. Mr. Sienbenthal has carefully 

 considered and tested the numerous theories that have been put 

 forward from time to time by other observers, and has come to the 

 conclusion that the ores were segregated by artesian — circulating 

 alkaline — saline sulphuretted waters from zinc and lead minerals 

 disseminated in the Cambrian and -Ordovician limestones of the 

 Ozark uplift, which is a low asymmetric dome, rudely elliptical in 

 outline, lying in southern Missouri, northern Arkansas, south- 

 eastern Kansas, and north-eastern Oklahoma. The great mass of 

 the ores appear to have been conveyed as bicarbonates, and to have 

 been precipitated as soon as the water bearing them reached the 

 surface and gave up the carbonic acid dissolved in it. The data 

 upon which his conclusions are based are very fully set forth. The 

 memoir is one that should be studied by all those interested in the 

 question of the genesis of ore deposits. 



