Symposium on Archaean rocks

88 matic radiative equilibrium, which postulates that every quantum of radiation maintains its identity from the moment of its emission at the nuclear star until if finally escapes from the surface of the nebula. I suddenly realized that this implicit assumption was inconsistent with the intensity of the Balmer lines of hydrogen. I developed a theory of nebular excitation by fluorescence: Absorption of ultraviolet radiation by hydrogen atoms, which then produce the Balmer lines as a cascade phenomenon. From this hypothesis I derived high temperatures for the exciting nuclear star. Zanstra, subsequently but independently, developed a similar principle. He and I long ago agreed that we should not apply the principle of priorities. We further urged that the basic principle should henceforth be known as the Zanstra-Menzel or the MenzelZanstra mechanism. Chapter 3 deals with the distances and dimensions of planetaries. It discusses various methods of parallax determination, including that derived from astrophysical arguments. Here, again, the author fails to mention the pioneer work of this reviewer. Chapter 4 concerns itself with the temperatures of both the nuclear and the nebular gas. The discussion is interesting and adequate. Chapter 5 turns toward the difficult problem of continuous emission from the nebular gas, with the discussion centered primarily on two-quantum emission and the possibility of synchrotron radiation. Chapter 6 treats the problems of radiative equilibrium. Chapter 7 goes deeply into the problem of nebular structure, especially that of nebulae having double envelopes. Chapter 8 deals with problems of stability of gaseous envelopes. In Chapter 8, Gurzadyan presents the arguments favoring the presence of magnetic fields in planetaries. The discussion is original and convincing. The final Chapter 9 considers problems of nebular origin. The author rejects the once popular idea that planetaries are the result of nova or suparnov~activity. Similarly he argues that they cannot be the product of slow emission of Wolf-Rayet stars. He favors the idea that the nuclei of planetaries are "newborn stars", and that the gaseous envelopes represent excess .mass ejected from the star. The concept is interes-

ting, but his objections to a slow-nova process are not well founded. I have found this book interesting and stimulating. However, the references to the work of others, voluminous as the list seems to be, is very incomplete. D.H. Menzel, Cambridge, Mass.

ARCHAEANGEOLOGY J.E. Glover (Editor), 1971. Symposium on Archaean Rocks. Special Publication No. 3, Geological Society of Australia, 469 pp., Aus. $ 6 . 0 0 (members); 12.00 (non-members). (Available from The Assistant Secretary, Geological Society's office, Gemmology House, 24 Wentworth Avenue, Sydney, N .S.W. 2010). This volume, containing 33 papers and 20 abstracts presented at a Symposium in Perth during May, 1970, provides an opportunity for the consideration of general problems of Archaean geology and the presentation of the results of current Australian research, particularly in. Western Australia. The opening address by Professor Sutton provides an admirably brief survey of the current state of knowledge of Archaean geology, interwoven with his own thoughts on early crustal development. Rankama (in an abstract) focusses attention on the problems of defining Archaean as a chronostratigraphic term, and it is therefore perhaps not surprising that an account, albeit in abstract, of the Sudbury irruptive found its way into a volume on Archaean geology. However, the majority of authors appear to subscribe to Sutton's view that Archaean defines that period in time during which the crust was tectonically metastable and reflects a particular stage in crustal development, although not all would accept Sutton's upper limit of +- 2.7 b.y. for the Archaean. The contents are divided into six sections under the headings: (i) geochronology and development of the Earth's crust; (ii) regional geology; (iii) economic geology; (iv) serpentinites; (v) tectonics; and (vi) special aspects. In the first section opposing views on crustal development are presented by Windley and Bridgwater on the one hand and Anhaeusser

89 on the other, while White and his co-authors discuss the hypothesis of sea-floor spreading in the Archaean. Summaries of Australian geochronological data are presented in other papers in this section that will provide a useful reference. Metallogenic patterns in the Canadian Shield, the classification and genesis of nickel deposits, and the statistical investigation of unit regional value of natural resources as a measure of potential for development of large regions are subjects discussed in the economic geology section. The last-mentioned topic, presented in a paper by Griffiths and Singer, is of interest to economists and government planning agencies as well as geologists, and may well stimulate exploration companies to reassesstheir prospecting strategy. The importance of ultramafic rocks in Archaean greenstone terranes is emphasized by the devotion of an entire section to the subject of serpentinites, their genesis, evolution, and crystallization histories. O'Driscoll and Stowe discuss some of the broader implications of tectonic development in Western Australia and Rhodesia, respectively, while Hopgood proposes that complexly deformed, Precambrian gneissic terranes may be correlated by considering the sequences of deformational events that have affected them. The last section entitled "Special aspects" includes consideration of oxygen isotopes in geothermometry, organic matter in Archaean rocks, the evolution of the deep continental crust, and Archaean sedimentation. One of the most important aspects of symposia is that a number of specialists are brought together enabling them to hold discussions with other workers in similar or related fields. It is therefore disappointing to find that the discussion that must have been provoked among the 595 participants at this symposium, following the presentation of the papers, is not recorded. This is a feature common to many symposia and may well be an aspect that could be given greater attention in the future. This criticism, however, does not detract from a volume that contains much basic information, and should serve as a useful work of reference to Australian Precambrian geology, in particular, and to Precambrian geology in general. D.R. Hunter, Johannesburg

WATER QUALITY IN A STRESSED ENVIRONMENT Wayne A. Pettyjohn (Editor), 1972. Readings in Environmental Hydrology. Burgess, Minneapolis, Minn., 309 pp., U.S. $ 4.95. Environmentalists, teachers, hydrologists, students, researchers and citizens, in general, owe a debt of gratitude to Dr. Pettyjohn for bringing together these many selections into one readily available volume that provides a background and introduction to this important topic, for which no standard text exists. Although at the time of original publication many of the articles were read by hydrologists, particularly those interested in the chemistry of water, it is enlightening at one sitting to read a historical overview o f the subject written by such people as H.E. LeGrand, Morris Deutsch, Graham Walton, and H ,V. Warren, who were among the first to articulate their thoughts regarding an environmental crisis associated with water pollution. The book is divided into six parts, which provides a nice balance between technical background, case studies, and recommendations for future action. Most o f the papers touch on all three aspects, but it is possible to select several that should be studied by the nonhydrologist for a clearer insight into the hydrologic principles that control pollution. Particularly recommended are papers by LeGrand, Deutsch, R.H. Brown, and William J. Schneider on geologic controls and groundwater pollution; by Berlie L. Schmidt on agricultural sources of water pollution; and by Harry Warren and Robert Delavault on the effects of pollution by trace elements in areas of mineral development. The editor has also wisely selected several papers that provide necessary background to evaluate the case studies. These are the papers in Part 1 on Water Quality Criteria, prepared by a committee o f the Federal Water Pollution Control Administration in 1968; the paper by C.H. Durfor and Edith necker on constituents and properties; and the paper by W.H. Durum, J.D. Hem, and S,G. Heidel on the reconnaissance o f minor elements in surface waters in the United States. My recommendation to the serious reader would be to study these three papers before reading the