"The first phase of geophysical exploration is carried out on the subsurface.The subsurface in this phase is inaccessible to direct observation. D.W. Strangway presents an interesting and effective method: audiofrequency magnetotelluric (AMT) sounding. In the second phase where observations can be made, D.J Buchanan writes of fault detection in coal seams, and A. Hussain writes about of gravity surveys.Other contributions include, improvement of geophysical logs by filtering and a troublesome problem which can appear in either phase of exploration-discovery and exploration of caves and abandoned mine workings.'

This is a collection of original papers, each by an expert in his field. They deal with different sectors of recent geophysical development. It may be, at first, difficult to see what else unites them, and how these several technologies can contribute to an integrated exploration process. What brings these writers together is that they have all contributed to the improvement of what comes to the eye of the geophysical interpreter. Some of the improvement is achieved at the data-gathering stage, some of it in processing, and in presentation. For all of this improvement interpreters in general are most grateful. The editor is appreciative in a quite personal way, not only of the advances in technology, but also of the effort in writing which has been made by these busy contributors, and so created this collection. Something can be said here about interpretation and the environment in which it is carried out, since it represents the field where the results of these technical developments are ultimately tested. In the commercial world it is from the geophysical interpreter that management learns the results of a large sector of exploration expenditure, and learns them in a form on which still larger expenditures on later phases of exploration can be based.

As a slag heap, the result of strip mining, creeps closer to his house in the Ohio hills, fifteen-year-old M. C. is torn between trying to get his family away and fighting for the home they love.

Developments in Economic Geology, 5: Principles of Induced Polarization for Geophysical Exploration focuses on the principles, methodologies, and approaches involved in induced polarization (IP), including anisotropism, electromagnetic coupling, and electrical circuits. The book first takes a look at resistivity principles, theory of IP, and laboratory work in IP. Concerns cover electrical measurements of rocks, anisotropism, early part of decay curve and the comparison with frequency effects, electrical models of induced polarization, electrical polarization, resistivities of earth materials, and resistivity exploration methods. The manuscript then elaborates on IP field equipment, telluric noise and electromagnetic coupling, IP field surveying, and drill-hole and underground surveying and the negative IP effect. Discussions focus on differences between surface and subsurface methods, current-sending system in the field, telluric (earth) currents, electromagnetic coupling, design considerations, coupling of electrical circuits, design considerations, and signal-generating system. The manuscript ponders on the complex-resistivity method and interpretation of induced-polarization data, including grade estimation of mineralization using the IP method, complex-resistivity survey, signal detection capabilities of the complex-resistivity method, and disadvantages of the complex-resistivity method. The text is a valuable source of information for researchers wanting to study induced polarization.

One of the themes in current geophysical development is the bringing together of the results of observations made on the surface and those made in the subsurface. Several benefits result from this association. The detailed geological knowledge obtained in the subsurface can be extrapolated for short distances with more confidence when the geologi cal detail has been related to well-integrated subsurface and surface geophysical data. This is of value when assessing the characteristics of a partially developed petroleum reservoir. Interpretation of geophysical data is generally improved by the experience of seeing the surface and subsurface geophysical expression of a known geological configuration. On the theoretical side, the understanding of the geophysical processes themselves is furthered by the study of the phenomena in depth. As an example, the study of the progress of seismic wave trains downwards and upwards within the earth has proved most instructive. This set of original papers deals with some of the more vigorous developments in subsurface geophysics: and it is hoped that it will contribute to the understanding of geophysical phenomena in the solid. The editor thanks the busy workers in the several fields who have made time to produce these contributions.

This new edition of the well-established Kearey and Brooks text is fully updated to reflect the important developments in geophysical methods since the production of the previous edition. The broad scope of previous editions is maintained, with even greater clarity of explanations from the revised text and extensively revised figures. Each of the major geophysical methods is treated systematically developing the theory behind the method and detailing the instrumentation, field data acquisition techniques, data processing and interpretation methods. The practical application of each method to such diverse exploration applications as petroleum, groundwater, engineering, environmental and forensic is shown by case histories. The mathematics required in order to understand the text is purposely kept to a minimum, so the book is suitable for courses taken in geophysics by all undergraduate students. It will also be of use to postgraduate students who might wish to include geophysics in their studies and to all professional geologists who wish to discover the breadth of the subject in connection with their own work.