vi PREFACE 



description of procedures and instruments used in geophysical science is 

 limited to those having a direct bearing on geophysical exploration. A 

 chapter on the history of geophysical exploration was abandoned in favor 

 of a few historical references. The material is arranged in methodical 

 rather than historical order. 



A table of symbols precedes each major chapter dealing with methods 

 that represent a geophysical entity. This applies to gravitational, mag- 

 netic, seismic, and electrical methods (Chapters 7 through 10). In these 

 chapters the discussion follows a uniform plan. First is an outline of 

 fundamentals, followed by a description of rock properties and rock-testing 

 methods. Instruments and instrument theory, as well as corrections and 

 interfering factors, are reviewed next. The treatment is concluded in each 

 case with a derivation of the fundamental interpretation equations and a 

 description of surveys made on known geologic conditions. 



Various individuals and organizations have assisted in the preparation of 

 this book. Specific acknowledgment is made on the following page. 



C. A. Heiland 



