Abstracts of Bell System Technical Papers Not Appearing in this Journal (01 July 1928)

Dence against a face of a nickel crystal, and observations were made upon the diffraction beams which issued from the incidence side of the crystal at various critical speeds of bombardment. It was anticipated that if the angle of incidence were made other than zero a beam of electrons would be found issuing from the crystal at a series of critical speeds in the direction of regular reflection, and that the series of critical speeds would change with the incidence angle. 

This regularly and selectively reflected electron beam which is the analogue of the Bragg x-ray reflection beam has been found, and measurements have been made upon it. In the x-ray phenomenon the wave-length of the reflected beam at maximum intensity is related through a simple formula to the angle of incidence and a dimension of the reflecting crystal. This formula (Bragg's formula) does not obtain in the case of electron reflection because of the refraction of the electrons by the crystal. 

The departures from the Bragg relation are used to calculate indices of refraction of nickel for electrons of various speeds or wave-lengths. Introduction to Mathematics of Statistics.1 R . W . BURGESS. This book (282 pp.) discusses the best elementary methods of statistical analysis from the standpoint of a beginner who has had one year of college mathematics, or some practical statistical experience and the ordinary high school mathematics. "Statistical Analysis" is regarded in this book as the logical process by which large masses of quantitative facts may be classified, summarized, analyzed, and compared so as to yield reliable conclusions.