250 



NATURE 



[November 5, 19 14 



work of the atmosphere, of overground and 

 underground waters, and of snow and ice, 

 vulcanism and the movements of the earth's 

 crust, and the nature and arrangement of rock- 

 types and rock-masses. The second part, of some 

 400 pages, deals with historical geology. This 

 should be of great service to students, especiallv 

 those outside America, by providing a generalised, 

 but not too brief account of the stratigraphy of 

 North America, a subject of which no very satis- 

 factory digest has hitherto been available. A 

 classification of geological time into five eras is 

 adopted — archeozoic, proterozoic, paleozoic, 

 mesozoic, and cenozoic — and the description of 

 the first of these is preceded by a discussion of 

 the origin and constitution of the earth on the 

 Laplacian and planetesimal theories respectively. 



This part of the book is illustrated by numerous 

 maps, sections, and figures of fossils, most of 

 which are good. But the eighteen full-page maps 

 showing the outcrop, underground extent, and 

 eroded areas of the several systems in America 

 are so largely conjectural that it is a question 

 whether a single geological map in colours show- 

 ing the actual outcrops, as at present known, 

 would not have been more suitable and useful 

 in a book of this kind. Many of the sections, 

 especially those taken from the publications of 

 the U.S. Geological Survey, seem unnecessarily 

 detailed, and have suffered by reduction : their 

 educational value might have been greater if they 

 had been redrawn in ^ more diagrammatic form. 



The book is an admirable statement of physical 

 and stratigraphical geology from the American 

 point of view, and will doubtless be warmly wel- 

 comed and much used by students and general 

 readers for many years to come. 



(2) This volume is based upon the courses in 

 geology which the authors have been giving, for 

 some years past, to students of engineering. The 

 scope of the work is wide, and its treatment 

 fuller than in most books on the subject which 

 have hitherto appeared. 



Chapters dealing with the minerals of rocks, 

 and with the occurrence and origin of the rocks 

 themselves, are followed by one on tectonics and 

 metamorphism, in which the importance of joint- 

 ing, cleavage, folding, faulting, and other rock 

 structures in engineering op)erations are fully 

 dealt with. This is succeeded by a chapter on 

 rock-weathering and the formation of soils. The 

 next two deal with surface and underground 

 waters, and here the geological principles under- 

 lying water-supply, drainage, the sinking of wells, 

 the construction of reservoirs, etc., are thoroughly 

 discussed. A short chapter on landslides follows, 

 and then two on the action of waves and currents 

 ■wn o-j/in Arm c\a~\ 



in seas and lakes, and its bearing upon coastal 

 erosion and harbour construction. The origin and 

 economic uses of glacial deposits are then de- 

 scribed. The remaining chapters deal with 

 specific materials of importance to the civil or 

 mining engineer, such as building stone, lime, 

 cement, plaster, clay, fuels, road foundations, and 

 road metals ; the last chapter, intended for the 

 metal miner, consists of a short account of the 

 general principles of ore-formation and of the 

 geology of certain of the useful metals. This, 

 from limits of space, is necessarily somewhat in- 

 adequate. 



At the end of each chapter useful references are 

 given to additional literature on the subject therein 

 dealt with. The book is well illustrated, and there 

 is a triple index referring to subjects, localities, 

 and authors. It is undoubtedly a useful addition 

 to what has already been written on engineering 

 geology. It is eminently practical, and its very 

 direct application to a great variety of engineering 

 problems should commend it, not only to students, 

 but also to engineers in actual practice. 



C. G. C. 



APPLIED ELECTRICITY. 

 (i) Alternating Currents and Alternating Current 

 Machinery. By Prof. D. C. Jackson and Dr. 

 J. P. Jackson. New edition, rewritten and 

 enlarged. Pp. ix + 968. (New York: The 

 Macmillan Company ; London : Macmillan and 

 Co., Ltd., 1913.) Price 2t^s. net. 

 (2) The Elements of Electricity. By Prof. Wirt 

 Robinson. Second edition. Pp. xv -f 596. 

 (New York : John Wiley and Sons, Inc. ; Lon- 

 don : Chapman and Hall, Ltd., 1914.) Price 

 I05. 6d. net. 

 (i) T N its thirteen chapters, this work covers 

 X fairly thoroughly the ground suggested 

 by its title ; in most places the theoretical side is 

 treated with at least sufficient detail, but the con- 

 structional side has also received a good share of 

 attention. We should have liked a somewhat 

 fuller discussion of the motor-converter, and think 

 the time is also ripe for some mention of the Kapp 

 and Scherbius phase advancers and of the Hunt 

 Cascade motor. The first few chapters impressed 

 us very favourably, and although we were some- 

 what disappointed with the later chapters, we 

 consider the book a good one, which will be of 

 service to advanced students. 



From the very beginning, the authors use the 

 complex quantity, but it is not until chapter v. 

 that we get a full explanation of the method. 

 This chapter is an excellent one, but should have 

 come earlier. The numerical examples given 

 (single-phase problems) show well the use of the 



