Gilbert Swift, a native of Brooklyn, New 

 York, received a B.S. degree in electrical 

 engineering from the University of Pennsyl- 

 vania in 1933, and a Professional Electrical 

 Engineering degree in 1949. He has been em- 

 ployed by Well Surveys, Inc., since 1940, and 

 is at present in charge of radioactive well- 

 logging interpretation research. During World 

 War II, he served as Officer in Charge, Direc- 

 tion-finding and Intercept Section of the Sig- 

 nal Corps Engineering Laboratories. Mr. 

 Swift is the author, or co-author of a number 

 of papers pertaining to radioactivity well 

 logging. 



Maurice Pierre Tixier was born in Cler- 

 mont, France. He was graduated from the 

 Ecole d'Arts et Metiers d'Erquelinnes (Bel- 

 gium) in 1932 and from the Ecole Superieure 

 d'Electricite in 1933. During 1934 and 1935, 

 he worked as a field engineer for Societe de 

 Prospection Electrique, Paris. He came to 

 work for Schlumberger Well Surveying Cor- 

 poration in 1935 and was Manager of the 

 Rocky Mountain Area from 1941 to 1949. He 

 is now Field Development Manager at the 

 company headquarters in Houston, Texas. He 

 has written many papers on technical subjects. 



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