CONTRIBUTORS TO THIS ISSUE 235 



Vice President, 1922-25. Manufacturers Junction Railway, Vice 

 President, 1922-25. American Telephone and Telegraph Company, 

 Vice President, and Bell Telephone Laboratories, President, 1925-. 

 Dr. Jewett is a Past President of the American Institute of Electrical 

 Engineers. 



Francis F. Lucas, Associated Bell Telephone Companies, 1902-10; 

 Western Electric Company, 1910-25; Bell Telephone Laboratories, 

 1925-. Mr. Lucas has specialized in the development and appli- 

 cation of microscopy. He has received international recognition 

 and awards for the development of high power metallography and 

 ultra-violet microscopy and for numerous scientific papers which he 

 has contributed on the subjects of metallurgical and biological re- 

 search. For several years he has been Consulting Technical Expert 

 for the War Department, U. S. A., Watertown Arsenal. 



Edward L. Nelson, B.S. in E.E., Armour Institute of Technology, 

 1914; Western Electric Company, 1917-25; Bell Telephone Laborato- 

 ries, 1925-. As Radio Development Engineer of Bell Telephone Lab- 

 oratories, Mr. Nelson is responsible for the development and design of 

 commercial radio apparatus, which includes radio broadcasting equip- 

 ment. 



R. L. Wegel, A.B., Ripon College, 1910; Assistant in Physics, 

 University of Wisconsin, M. A., 1910-12; Western Electric Company, 

 1914-25; Bell Telephone Laboratories, 1925-. Mr. Wegel has written 

 several papers on theory of telephone receivers and on the theory of 

 hearing. The article appearing in this issue is taken from lecture 

 notes on Mechanics of Vibrating Systems by the author. It is planned 

 to publish these notes in future issues of the Bell System Technical 

 Journal. 



M.K. ZiNN, B.S. in E.E., Purdue University, 1918; American Tele- 

 phone and Telegraph Company, 1919-. Mr. Zinn's work has been 

 related particularly to the design of loading for telephone circuits. 



