PERHAPS some apology, or at least explanation, is necessary for the choice of a subject for which I have not even been able to find a satisfactory title. Applied geophysics may clearly be taken to include certain aspects of meteorology or oceanography, or, indeed, any branch of knowledge in which physics is applied, in the service of mankind, to the elucidation of the properties of the earth. I propose to deal with what is in fact only a limited field of work. Put briefly, it covers the application of physical methods to the examination, without digging or boring, of what lies beneath the surface of the earth at relatively shallow depths of less than a few thousand feet. The application is more particularly directed to the discovery of deposits of economic importance, such as minerals or oil, or the structural formations with which they are likely to be associated.