12 EXPLORATION GEOPHYSICS 



interest in the study of earthquakes. In addition to his studies of natural 

 earthquakes, Mallet in 1851 produced artificial earthquakes by exploding 

 gunpowder and investigated the effects with a crude seismometer com- 

 prising a tray of mercury and a small telescope. He also suggested employ- 

 ing this method to study the earth's immense water-covered areas. 



In 1888, A. Schmidt, on the basis of Mallet's work, suggested that time- 

 distance graphs of artificial earthquake waves could be used to study the 

 variation of velocity with depth. 



One of the early papers (1889) which is of special interest is that of 

 Fouque and Levy, describing certain experiments whereby they deter- 

 mined the velocity of seismic waves in various kinds of rocks. They used 

 gimpowder and dynamite to create seismic waves in some of these experi- 

 ments, while in others they utilized a large stamping machine weighing 

 100 tons. A dish of mercury served as their seismometer. Photographic 

 registration on a moving plate was accomplished by focusing a concen- 

 trated beam of light on the surface of the mercury, from which it was 

 reflected to the photographic plate. Telephonic communication was used in 

 many of their experiments. Electrical firing of their explosive charge was 

 accomplished by discharging a Ley den jar through a spark gap in proximity 

 to gunpowder. 



In the early part of the twentieth century, Belar, von dem Borne, 

 Benndorf, Galitzin, and others suggested the use of artificial explosions 

 for studying subsurface structure. Prince Boris Galitzin perfected the 

 galvanometric seismometer with magnetic damping which bears his name. 

 The results of Galitzin's investigations were published in a volume, Seismo- 

 metrie, in 1911. A revised edition of Galitzin's work, translated into 

 German, has become one of the classics of the science. 



The Refraction Technique. L. P. Garrett, apparently the first to see 

 the possibility of using refraction methods for locating salt domes, con- 

 ducted investigations during the years 1905-1906 and made the first suc- 

 cessful commercial application of refraction technique in 1923. Dr. L. 

 Mintrop experimented with a mechanical seismograph during World 

 War I. Working with Wiechert in Gottingen, he perfected his instrument 

 and technique so that in 1919 he was able to secure a basic patent, later 

 revoked, on the seismic method for determining subsurface structure. The 

 first discovery of oil resulting from use of this method was on the Orchard 

 Dome in Fort Bend County, Texas, by a crew of Mintrop's under the 

 direction of Alexander Deussen, in 1924. This seemed, and later proved 

 to be, an ideal method to use on the Gulf Coast in the search for shallow 

 salt domes. There the rocks possess fairly tmiform and low velocities 

 which are in marked contrast with the high velocities of the intruding salt 

 dome. The rapidity of this method and the positive character of its results 

 surpassed those of earlier torsion balance methods. This method became 

 obsolete as a leading exploration tool after about six years. However, as 



