Contributors to this Issue 



O. B. Blackwell, B.S. in Electrical Engineering, Massachusetts 

 Institute of Technology. After graduation, he entered the Engineer- 

 ing Department of the American Telephone and Telegraph Company 

 and in 1919 was made Transmission Development Engineer. Mr. 

 Blackwell has general supervision of transmission developments and 

 has been prominently associated with progress in long distance wire 

 and radio telephony. 



Karl K. Darrow, B.S., University of Chicago, 1911; University 

 of Paris, 1911-12; University of Beriin, 1912; Ph.D., University of 

 Chicago, 1917; Western Electric Company, 1917-25; Bell Telephone 

 Laboratories, 1925-. Dr. Darrow has been engaged largely in writing 

 on various fields of physics and the allied sciences. Some of his earlier 

 articles on Contemporary Physics form the nucleus of a book entitled 

 "Introduction to Contemporary Physics." 



Clifford E. Fay, B.S. in Electrical Engineering, Washington Uni- 

 versity, 1925; M.S., 1927. Bell Telephone Laboratories, 1927-. Mr. 

 Fay has been engaged principally in the development of power vacuum 

 tubes for radio purposes. 



J. B. Johnson, B.S., University of North Dakota, 1913; M.S., 

 University of North Dakota, 1914; Ph.D., Yale, 1917; Engineering 

 Department, Western Electric Company, 1917-25; Bell Telephone 

 Laboratories, 1925-. As Research Physicist, Dr. Johnson has been 

 engaged in the development and application of special vacuum tubes 

 and gaseous discharge devices. 



Frederick B. Llewellyn, M.E., Stevens Institute of Technology, 

 1922; Ph.D., Columbia University, 1928. Western Electric Company, 

 1923-25; Bell Telephone Laboratories, 1925- Dr. Llewellyn has 

 been engaged in the investigation of special problems connected with 

 radio. 



D. A. McLean, B.S. in Chemical Engineering, University of Colo- 

 rado, 1929. Bell Telephone Laboratories, 1929- Mr. McLean's 

 work in the Chemical Research Department has dealt principally with 

 plasticity and viscosity studies of various materials. 



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