PREFACE TO SECOND EDITION 



Ten years have passed since the manuscript for the first edition of Exploration 

 Geophysics was prepared. During this period geophysical exploration has progressed 

 from an interesting tool used by relatively few into a world-wide art recognized as a 

 basic technique for subsurface exploration. A major portion of the oil fields discovered 

 during the past decade can be credited wholly or in part to geophysics. The monetary 

 value of these fields is many times the cost of the geophysical work which preceded 

 their discovery. During this same period the professional status of the geophysicist has 

 been established. His basic technical knowledge and mathematical training have been 

 found to be essential spokes in the wheel of modern exploration. These spokes will 

 carry more and more of the load as the exploration wheel revolves toward the problems 

 of future development. 



The phenomenal success record established by exploration geophysics is a tribute 

 to the inventiveness, scientific ability, integrity, and perseverance of the personnel 

 engaged in this work. Too much credit cannot be given to those men. They have built 

 up the industry by their high professional standards. Coupled with these attributes are 

 the good business judgment and fine public relationships of the administrators in the 

 profession. By and large, the industry has had few subsidies. The advances in tech- 

 nique and improvements in instrumentation have been brought about largely by the 

 ventured capital of private enterprise. Healthy competition within the industry has 

 required that skillful use be made of allied technical advances in such fields as physics, 

 electronics, transportation and communication. 



In an effort to provide a text of broad scope which would be of greater service 

 both to the student and to the practicing geophysicist and geologist, the 1940 edition 

 of Exploration Geophysics has been revised. So many changes in technique and instru- 

 mentation have taken place since the book was first published that the revision has been 

 a task very nearly equalling that of the original compilation. The major portion of the 

 book has undergone complete rewriting, in order to include the important developments 

 of the past decade. Every effort has been made to create a text which not only presents 

 background and theory, but also shows in a practical manner how these fundamentals 

 may be applied to the problems of exploration. 



Our grateful thanks are extended to the consultants and the personnel of the many 

 companies and institutions who have so generously contributed new material or collab- 

 orated in the revision and criticism of the manuscript. An attempt has been made in 

 the list of Contributors and Collaborators to give recognition to these co-workers and 

 to indicate the subject matter of their contributions. Without the help of these men, 

 an up-to-date and comprehensive edition would scarcely have been possible. The author 

 has reworked their data and manuscript material as was necessary to integrate it into 

 the remainder of the text. In many cases this reworking has shifted the original 

 emphasis, and the recognition accorded the various collaborators does not necessarily 

 mean that they individually endorse the text as published. The final decision has rested 

 with the author and is based upon his training and experience. 



Special mention must be made of the work of Dart Wantland and Joshua Soske, 

 who have given most freely of their time and energy. It is also a pleasure to acknowl- 

 edge the work in the non-technical phases of the revision, particularly to Helen Murphy 

 for her painstaking assistance in editing and compiling the manuscript and to Dorothy 

 Stark who made the drawings and gave valuable aid during the compilation of the text 

 and index. Clyde H. Wilson and Herbert Leifer contributed many helpful suggestions 

 during reading of the manuscript. 



Los Angeles 24, Calif., /. /. JAKOSKY. 



December, 1949. 



