686 BELL SYSTEM TECHNICAL JOURNAL 



did the transmitter deviate from its assigned frequency by more than 

 ± .01 per cent, whereas the Hmitation specified by the Federal Radio 

 Commission is ± .05 per cent. 



On the Art of Metallography.* Fraxcis F. Lucas. Photomicro- 

 graphs showing the highest degree of resolution and detail as yet ob- 

 tainable with the high power microscope illustrate the paper. 



Of particular interest is the new theory of the cause of fatigue failure 

 in hardened steel presented by Dr. Lucas as due to the presence of 

 minute cracks produced during the hardening process. 



These quenching cracks average 25 atoms in width and 1000 atoms 

 in length. 



A complete description of the use and potential resolving ability 

 of the high power microscope leads up to the art of metallography and 

 its value in the industrial field. 



Announcement is also made of the new metallurgical equipment by 

 means of which can be achieved crisp, brilliant images at twice the 

 present limits of useful magnification. The order of resolution will be 

 improved and better optical and mechanical means will be at the dis- 

 posal of the metallographer. 



Some Physical Factors Affecting the Illusion in Sound Motion Pic- 

 tures.^ Joseph P. Maxfield. The advent of sound pictures brought 

 the physicist and engineer face to face with problems which lie in the 

 field of art as well as in the field of material things. A study of the 

 physical factors which underlie art would probably be lengthy although 

 it is conceivable that with sufficient knowledge of these physical factors 

 it might be possible artificially to develop high-grade artistic sound 

 pictures. It was felt, however, that more useful information of im- 

 mediate applicability could be obtained by attempting to control, 

 under the conditions of photography and recording, those factors which 

 determine an observer's interpretation of what he sees and hears when 

 observing a real event. The artist and director must be relied upon 

 for the art in the production and the engineer or physicist is required 

 to record and reproduce the scene in such a manner that the illusion in 

 reproduction transmits to the audience the artistry produced by the 

 actor. 



This paper therefore describes the results of an empirical study of 

 methods of controlling some of the factors available to the engineer in 



^ Presented at N. Y. nitg. of Amer. Itist. of Mining and Metallurgical Engineers, 

 February, 1931. Published in Heat Treating and Forging, July and August issues, 

 1931. 



* Jour. AcoHs. Soc. Anier., July, 1931. 



