IN the last few months a number of very welcome books have been published in the United States on the subject of geophysical prospecting. Of these, the present work fulfils a very useful purpose, as it is written mainly for the layman, that is the petroleum geologist and the petroleum engineer. These, as a rule, do not participate actively in this branch of oil prospecting; nevertheless they should be in a position to appreciate the possibilities and limitations of the various methods which can be employed for this purpose, and also they should be able to understand the implications of any geophysical survey. In such a subject as geophysical prospecting, in which the technique is advancing rapidly, there are obvious difficulties in the way of the layman who wishes to keep in touch with the latest developments. Nettleton's book, giving a reliable and co'ordinated picture of the present state of geophysical prospecting in relation to oil, should do much to remove these difficulties and to form a background against which future developments can be assessed. Geophysical Prospecting for Oil By L. L. Nettleton. Pp. xi + 444. (New York and London: McGraw–Hill Book Co., Inc., 1940.) 35s.