332 REVIEWS 



and paleontology. The volume is abundantly illustrated and both the 

 formations and the fossils afford excellent material for this purpose. A 

 full bibliography enhances the value of the volume. 



R. D. S. 



Mineral Resources of Michigan for igi4 and Prior Years. Pre- 

 pared under the direction of R. C. Allen. With a treatise on 

 Michigan copper deposits by R. E. Hore. Michigan Geo- 

 logical and Biological Survey, PubHcation No. 19, 1915. 

 Mineral Resources of Michigan for igiy and Prior Years. Prepared 

 under the direction of R. C. Allen. Michigan Geological 

 and Biological Survey, Publication No. 27, 1918. 

 These volumes were not received until late in 1920. The note- 

 worthy feature (besides the statistics on the copper and iron industries, 

 as well as on the non-metallic minerals) is the presence in the 19 14 

 number of a 150-page treatise on the Michigan copper deposits, by 

 R. E. Hore. This article serves as an excellent summary of existing 

 knowledge on these deposits, as well as giving the author's ideas on the 

 subject. Hore beheves the native copper is essentially a primary replace- 

 ment deposit from solutions (probably carrying the copper as the 

 chloride) which accompanied and followed the extrusion of the lavas. 

 A feature of the work is the presence of some thirty photomicrographs 



of polished sectons. 



D J. F. 



Field Methods in Petroleum Geology. By G. H. Cox, C. L. Dake, 

 and G. A. Muilenburg. First edition, pp. xiv+305- 

 McGraw-Hill Book Company, Inc., 1921. $4.00. 



Petroleum geologists, particularly those who are lacking in field 

 experience, will welcome this book. It treats chiefly of the recognition 

 of structural features favorable for the accumulation of petroleum, 

 and of map-making and the instruments used in making maps. It includes 

 the solution of geologic problems and the making of a geologic report. 

 Problems of a "resident geologist" are not included. Graphic solutions 

 of geologic problems are also omitted. It is assumed that the reader 

 has a knowledge of the fundamental principles of geology and mathe- 

 matics, including trigonometry. 



Chapter I contains a description of the large variety of instruments 

 used by geologists, and Chapter II outlines instrumental methods in 



