REVIEWS 48s 



the two rocks ; in torbanite they are regarded as gels composed of incipient 

 drops of petroleum and inorganic colloidal material, while in oil-shales the 

 organic portion of the gel is inspissated oil rich in nitrogen and heavier hydro- 

 carbons. 



The revision of the later sections of the book, which deal with field work, 

 has resulted in increased lucidity, which is all the more welcome as these 

 chapters are intended for beginners. Of the value of the book, not only as a 

 summary of present knowledge of the geological aspect of " petroleum," but 

 also as a textbook for those likely to be engaged on geological work in oil- 

 fields, there can be no doubt. In future editions this value would be enhanced 

 by the inclusion of references to the literature, which are conspicuously 

 absent from the present one. 



A. S. 



Field Methods in Petroleum Geology. By G. H. Cox, Ph.D., E.M., C. L. 

 Dake, M.A., and G. A. Muilenburg, M.A. (Pp. xiv -f 305, with 

 50 text- figures) . (New York: McGraw-Hill Book Company, 1921. 

 Price, 245. net.) 



In the oil industry, more than in any other, has the value of the geologist 

 been recognised, and it is mainly due to this fact that we owe the already 

 large number of books on the subject of oil geology. While most of the latter 

 are concerned with the purely geological aspect of oil, and deal with the 

 theories of origin and the mode of accumulation, the book under review is 

 more directly concerned with the actual field work, especially from the point 

 of view of surveying. Indeed, only some forty-five pages are devoted to any 

 geological discussion, the remainder being devoted to a description of sur- 

 veying instruments and the methods of utilising these in reconnaissance 

 work and detailed surveys. 



The instruments described include the compass, level, barometer, alidade 

 and plane-table, and an adequate account of each is given. This is followed 

 by the application of these to the determination of distance, elevation, and 

 structure, while the last chapter deals with the details of field operations in 

 general. The treatment throughout is clear, and very complete, while the 

 numerous diagrams are of much aid in the understanding of the text. Not 

 only is there an excellent balance between theory and practice, but the book 

 abounds in hints of a very practical nature, many of which are the result of 

 wide field experience. Although the book is intended for workers in oil- 

 fields, it should prove very useful to geologists in general, especially those 

 who have to carry out survey work in unmapped countries. 



A. S. 



GEOGRAPHY 



Map Projections. By A. R. Hinks, C.B.E., M.A., F.R.S. Second Edition, 

 revised and enlarged. [Pp. xii -1- 158, with 21 illustrations.] (Cam- 

 bridge : at the University Press, 1921. Price, 12s. 6d. net.) 



Mr. Hinks' s book on Map Projections is too old a friend to need much in the 

 way of review. But it is very satisfactory that a second edition has given the 

 opportunity for it to be brought up to date, and enabled the author to give 

 us the benefit of the experience gained since the book was first written. 



Three new chapters have been added, dealing respectively with corrections 

 and additions to previous chapters, projections for topographical maps on 

 large scales, and the history of map projections. There are also some addi- 

 tional tables. 



It is unfortunate that the " corrections and additions " could not be 



