78 approximations for dealing with seepage forces are unsuitable if the permeability characteristics of the subsoil are complex, and that under these circumstances it would be advisable to construct a flow net. This is perhaps an unfortunate inference that complexity of subsurface conditions, often only poorly definable at best, can be reduced by invoking more complex analytical procedures. The book is, nonetheless, a valuable and outstanding contribution, helpful to the researcher, and extremely useful to anyone meaning to carry out stability studies and needing guidance through an extensive and sometimes inconsistent literature. R.B. Beck, Albuquerque, New Mexico BENTONITES Ralph E. Grim and Necip GQven, 1978. Bentonites - Geology, Mineralogy, Properties and Uses. Developments in Sedimentology, 24. Elsevier, Amsterdam, 256 pp., Dfl. 131.00, U.S. $ 57.00. This book is a notable contribution to the geology and mineralogy of bentonites and of the smectites, mainly montmorilIonites, which are the principal clay minerals in bentonites. Ralph Grim has had a long acquaintance with these materials throughout the world and chapter 3, which occupies a major part of the book, pp. 13--160 or 58%, summarizes his extensive knowledge of their geology. Chemical analyses by atomic absorption spectrometry, cation exchange capacities, amounts of extractable cations, and X-ray data limited to (001) and (06), (33) spacings are tabulated for 85 carefully chosen samples. These appear to be new data and the experimental procedures are fully described. Chemical analyses for 152 other samples also are tabulated. To obtain structural formulae, the authors prefer the method of fixed cationic numbers, ideally four tetrahedral and two octahedral cations per formula unit. They state (pp. 150,151) that this method 'does not require an accurate analysis of exchangeable interlayer cations' yet they also mention the results of Foster (1951) which show that only when a correction is made for exchangeable Mg is the number of octahedral cations reduced to 1.99-2.01. Electron-optical data are given considerable prominence and reflect Dr. Gdven's interests in the diffraction study of smectites. Results obtained by TEM and by selected area, single crystal diffraction are reproduced for many samplcs. The chapter concludes with useful summaries of the geology of bentonites and the mineralogy, chemistry and crystal growth of smectites. Chapter 4 takes up the electron diffraction study of smectites in considerable detail and it requires a good acquaintance with diffraction theory to follow the arguments. This is the second longest chapter, pp. 161--216 or 22% of the book. The question whether electron diffraction by single crystals of montmorillonite can be considered in terms of a two-dimensional space group or must be treated as a threedimensional problem even though smectite crystals have regularity only in two dimensions is treated very fully. The conclusion that a three-dimensional consideration is necessary seems well established. Chapter5 dealing with properties and uses occupies no more than about 30 pages or 13% of the book. Much of the material is very similar to what is given in Grim's earlier books published in 1962 and 1968 and seems to have been only slightly up-dated. Most of the references cited are pre-1960 (in fact, 80%) and only five references are in the 1970's. As the authors state, properties are contingent on chemical composition, atomic structure and morphology. However, the properties which are important in many (or most) applications are viscosity, thixotropy, plasticity, shrinkage, bonding strength, etc., all of which involve clay-water relations. A chapter dealing specifically with clay--water and clay--organic interactions would have been a useful intermediate step between the fundamental crystal chemistry of smectites and their applications. Smectites as catalysts get no more than about one page of text; is the information locked up so firmly that only one reference can be cited (Grim. 1962)? I welcome this book for what it gives us, an excellent account of bentonite geology, 79 the chemistry and structure of smectites, and a detailed treatment of electron diffraction by these highly disordered layer structures, and regret that properties and uses receive much less attention. G.W. Brindley, University Park, Penn. PETROLOGY C.J. AIl~gre and S.R. Hart (Editors), 1978. Trace Element in Igneous Petrology. A Volume in Memory of Paul W. Gast. Developments in Petrology, 5. Elsevier, Amsterdam, 272 pp., Dfl. 121.00, $49.95. It is a welcome coincidence that the two major geo-science journals, Earth and Planetary Science Letters and Geochimica et Cosmochimica Acta , have separately published two special volumes on trace element geochemistry during 1978. The volume by E.P.S.L. dedicated to the late Paul Gast, which is published by Elsevier in a book form edited by AIl~gre and Hart, deals with the application of trace element geochemistry to the problems in petrology. The volume by G.C.A. is the proceedings of the international conference on trace element geochemistry held at Sedona, Arizona, in September 1977. The topics in the book were wellselected and thus providing a wide perspective view of petrology of earth's lithosphere based on trace element studies. The topics include studies on isotopes, both radiogenic and non-radiogenic, in addition to the trace element distribution studies in the narrower sense, benefiting to widen the scope of the volume. The papers cover the wide variety of magma species, rock formations and their genetic mechanisms as well as the wide chronological time range. It is also welcome that Hoffman and Hart have introduced the diffusion processes in isotope petrology, as diffusion coefficients, though not well determined yet, will be important, useful parameters like partition coefficients and radioactive decay constants in trace element petrology. Most papers, either review or original work, are written in comprehensive styles, yet keeping up with the highest professional levels. In the opening chapter, AIl~gre and Minster gave full presentation of generalized treatment of the models of trace element fractionation and also introduced an interesting symbol-presentation method of the models. However, overdose of generalization and symbol notations tends to make the reader dizzy with i's, n's, arrows and waves, and to my regret, the formulae and symbols in the chapter are not well utilized in the rest of the volume. On the other hand, important and promising methods such as S m - N d isotope study are little discussed in the volume (I found the word 'Nd isotopes' just twice and no data in the whole volume). Although Nd--Sm data are scarce, so far, the method will be competent with the other existing chronological methods with the advantage that it is readily connected to the rare earth distribution studies. The method atso has an advantage that the mother and daughter isotopes involved are more compatible with the crystal structures of many rock-forming minerals compared with those of other methods. Thus it might well be discussed in the introductory chapter. The mechanism and theoretical background of trace element partition is not discussed in this volume. In fact, the present status of the theoretical grounds of partition coefficients may be said as 'far from achieved yet' as AIl~gre and Minster noted. However, recent developments of theoretical and experimental studies shown in the proceedings of the Sedona Conference, for example, have made the nature of partition coefficients much clearer as ever, at least in setting limitation of their use in petrological problems. In the sense, I recommend to keep the two volumes together in a bookshelf. I acknowledge the editors of both volumes for publication of the two contrasting, complementary works. Hiroshi Nagasawa, Tokyo GEOTECHNICAL ENGINEERING Alois Myslivec and Zdenek Kysela, 1978. The Bearing Capacity o f Building Foundations. Developments in Geotechnical Engineering, 21. Elsevier, Amsterdam, 237 pp., Dfl. 91.00, U.S. $ 39.75.