ABSTRACTS OF TECHNICAL ARTICLES 151 



have many points in common. Both deal in the last analysis with the 

 structure of matter and, in each, the microscope is an indispensable 

 tool. Improvements in microscopic vision which enlarge the world of 

 vision in one branch of science inevitably have a reflection in the other. 

 It is not the purpose of this paper to enter into a discussion of struc- 

 tures of living cells as revealed by the ultra-violet microscope. More 

 particularly, the object is to present a tool for biological research; a 

 tool which enables us to photograph the structure at different planes or 

 levels within a single cell or group of cells ; one which enables us to see 

 the living cell with a degree of precision and clarity not heretofore 

 possible by any other known means and with a potential resolving 

 ability at least twice that of the best apochromatic system using visible 

 light. 



Production of Plastic Molded Telephone Parts. ^ A. M. Lynn. The 

 Western Electric Company now manufactures for Bell System ap- 

 paratus a large number of different phenol-plastic, shellac, and hard- 

 rubber molded parts, the output of which varies from a few thousand 

 to several million per year. The majority of these molded parts are 

 produced in comparatively small quantities, but certain of them, such 

 as the phenol-plastic molded parts used in the hand-set type of tele- 

 phone, a new molded subscriber's set housing, and the receiver shell, 

 cap, and mouthpiece used on the older type of desk-stand telephone, 

 are hea\y-running parts. The tools and press equipment used in the 

 production of these parts are described in this paper. 



Variation of the Inductance of Coils Due to the Magnetic Shielding 

 Effect of Eddy Currents in the Cores.^ K. L. Scott. An analysis is 

 made of the shielding effect of eddy currents on the flux in the interior 

 of cores of cylindrical or flat sheet material. It is shown that the 

 counter voltage of self inductance of an iron-cored coil is due only to 

 the component of flux in the core which is in phase with the flux at 

 the surface of the core. Expressions are obtained and curves plotted 

 showing the variations of inductance of a coil with frequency, or with 

 the conductivity and permeability of the core material. Sample 

 calculations and some experimental results are given. The results 

 show that the inductances at high frequencies are actually less than 

 the predicted values, which leads to the suspicion that some factor 

 other than eddy currents causes the flux in the interior of the cores to 

 decrease with increasing frequency. 



5 Mech. Engg., Oct., 1930. 



6 Proc. I. R. E., Oct.. 1930. 



