432 BELL SYSTEM TECHNICAL JOURNAL 



The results indicate that the conductivity of a textile is practically 

 completely determined by three factors, the amount of absorbed 

 water, its specific conductance (as determined by the amount of 

 electrolytic material present in the textile) and its distribution. 



The Effect of Gases on the Resistance of Granular Carbon Contacts}^ 

 P. S. Olmstead. This paper describes a method whereby reproducible 

 measurements of the resistance of granular carbon contacts can be 

 made. The experimental arrangements were such that the resistance 

 could be measured as a function of gas pressure, applied voltage, 

 or time. 



Note on the Determination of the Ionization in the Upper Atmosphere}^ 

 J. C. ScHELLENG. This paper describes a method of estimating the 

 distribution of ionization in the upper atmosphere, based upon 

 measurements of the effective height determined by interference or 

 echo experiments. These two types of experiment are shown to give 

 identical results. 



Lead-Tin- Cadmium as a Substitute for Lead-Tin Wiping Solder}^ 

 Earle E. Schumacher and Edward J. Basch. In this paper data 

 are presented which show that certain lead-tin-cadmium alloys may 

 be advantageously substituted as solders for lead-tin alloys. Data 

 are given showing the physical and chemical properties of these alloys. 



New Specifications for Raw Materials}^ J. R. Townsend. In this 

 article the author points out that the annual demand for new telephone 

 apparatus by the Bell System requires a steady flow of materials of 

 the proper quality and uniformity into its manufacturing plants. 

 To meet this demand, a new set of engineering specifications has been 

 inaugurated to control these raw materials. A notable example of this 

 specification work is the preparation of Rockwell hardness and tensile 

 strength requirements for sheet brass, nickel silver and phosphor 

 bronze. The Western Electric Company, the Northern Electric 

 Company and one of the suppliers, the American Brass Company, 

 cooperated in this work. Rolling series were prepared covering all 

 grades, thicknesses and tempers. The requirements were based on 

 the data furnished by producer and consumer, and on experience over 

 a long period with commercial material. 



1° Journal of Physical Chemistry, Vol. 33, January, 1929, pp. 69-80. 

 ^^Proceedings of the I. K. E., Vol. 16, November, 1928, pp. 1471-1476. 

 ^'^ Lndustrial and Engineering Chemistry, Vol. 21, January, 1929, pp. 16-19. 

 ^^Instruments, Vol. 1, December, 1928, pp. 519-521. 



