ABSTRACTS OF TECHNICAL ARTICLES 373 



posited on one side of the tungsten ribbon and then made to migrate 

 to the other side of the ribbon. This migration occurred at an ap- 

 preciable rate above 1500° K and was not compHcated by evaporation 

 up to 1655° K. It was found that the migration coefficient depended 

 on / as well as on T. For a given set of conditions an approximate 

 value of the heat of migration was calculated to be 110,000 calories 

 per mol. 



Diffraction of Electrons by Metal Surfaces} L. H. Germer. Fast 

 electrons scattered from polished metal surfaces do not form diffraction 

 patterns. A strong Debye-Scherrer pattern is produced, however, by 

 electrons scattered from a surface which has been mechanically 

 roughened in such a manner that electrons are able to pass directly 

 through projecting irregularities. Small ridges extending from wires, 

 which have been drawn through an imperfect die, also give rise to a 

 diffraction pattern. These experiments indicate: (1) that there is no 

 considerable layer of amorphous material (Beilby layer) on a polished 

 metal surface, and (2) that Debye-Scherrer diffraction patterns are 

 formed only by transmitted electrons. Fast electrons scattered at a 

 small glancing angle from an etched polycrystalline surface form a 

 diffraction pattern if the surface appears mat or roughened, but no 

 pattern is formed if ths surface shows metallic luster. Here again 

 diffraction patterns appear to be produced only by transmission. A 

 probable explanation is given for the fact that diffraction rings are not 

 formed by electrons scattered from smooth polycrystalline surfaces. 



Perfect Transmission and Reproduction of Symphonic Music in 

 Auditory Perspective.^ F. B. Jewett, W. B. Snow and H. S. Hamil- 

 ton. The demonstration in Constitution Hall, Washington, on April 

 27th, of the perfect transmission and reproduction in full auditory 

 perspective of a symphony concert produced in Philadelphia by the 

 Philadelphia Orchestra and transmitted to Washington over under- 

 ground telephone wires, marked the completion of several years' work 

 by the research and engineering forces of the American Telephone and 

 Telegraph Company and Bell Telephone Laboratories. 



•In this paper is a foreword by Dr. Jewett. The features of the 

 demonstration and some description of the equipment are presented 

 by Mr. Snow. IMr. Hamilton discusses some of the details of the 

 complex line circuits used in the electrical transmission of the music. 



^Phys. Rev., May 1, 1933. 



^ Bell Telephone Quarterly, July, 1933. 



