CONTENTS xi 



CHAPTBR PAQK 



8. Magnetic Method (Cont.) 



III. Magnetic Instruments 318 



A. Construction Principles 318 



B. Prospecting Magnetometers 321 



C. Instruments for Regional Magnetic Surveys 355 



D. Observatory Instruments 366 



IV. Corrections 366 



A. Temperature 366 



B. Magnetic Variations 367 



C. Planetary Variation 372 



D. Base Change 372 



E. Influence of Iron and Steel Objects 373 



F. Terrain Anomalies 375 



G. Normal Fields 377 



V. Magnetic Fields of Subsurface Bodies (Interpretation Theory). . . . 377 



A. Graphical Representation of Results 377 



B. Qualitative and Quantitative Analysis 380 



C. Pole and Line Theory 381 



D. Induction Theory 389 



E. Interpretation Theory Based on Both Permanent and Induced 



Magnetization 400 



F. Model Experiments in Magnetic Interpretation 402 



G. Underground, Aerial, and Platform Surveys 404 



VI. Magnetic Surveys 408 



A. Magnetic Surveys in Mining 409 



B. Magnetic Surveys in Oil Exploration 422 



C. Magnetic Surveys in Civil and Military Engineering 433 



9. Seismic Methods 437 



I. Introduction 437 



II. Physical Rock Properties in Seismic Exploration; Selected Topics 



on the Theory of Elastic Deformations and Wave Propagation. . 441 



A. General 441 



B. Elements of Theory of Elastic Deformation and Wave Propa- 



gation 442 



C. Laboratory and Field Methods for the Determination of Elastic 



Moduli and Wave Velocities 452 



D. Factors Affecting Elastic Properties of Rocks 474 



E. Physical Rock Properties Related to Seismic Intensity 477 



III. Methods of Seismic I'rospecting 483 



A. Technique of Shooting; Shot Instant Transmission; Review of 



Seismic Methods 483 



B. Fan-Shooting Method 499 



C. Refraction Methods 504 



D. Reflection Methods 549 



IV. Elementary Theory and Description of Seismographs 579 



A. Classification 579 



B. Elementary Theory 580 



C. The Mechanical Seismograph 591 



D. The Electromagnetic Seismograph 592 



E. Review of Prospecting Seismographs 607 



