ABSTRACTS OF TECHNICAL ARTICLES 431 



Optical Conditions for Direct Scanning in Television.^ Frank Gray 

 and Herbert E. Ives. This paper discusses the conditions for 

 securing the maximum amount of light in a photoelectric cell placed 

 behind a television scanning disc when an image is formed on the 

 disc by a lens. Results obtained with a large scanning disc and a 

 lens forming images of sunlit objects are described. 



A Camera for Making Parallax PanoramagramsJ Herbert E. 

 Ives. This paper describes a camera for making transparencies 

 which when viewed through an opaque line grating show stereoscopic 

 relief through a wide range of distances and angles. The essential 

 feature of the camera is a mechanical coupling by means of which 

 the camera lens, the sensitive plate and grating, and the object 

 photographed, are kept in line as the camera moves from one side to 

 the other of the normal from the camera track to the object. 



European Factory Methods and Equipment in the Manufacture of 

 Metals.^ David Levinger. In this paper the author outlines his 

 observations of the metal-working industries of Europe, based on a 

 three months' tour of eight countries during the summer of 1927, 

 in which seventy-five industrial establishments were visited in England, 

 France, Germany, Belgium, Holland, Italy, Austria and Switzerland. 



Electrical Conduction in Textiles. Part I — The Dependence of the 

 Resistivity of Cotton, Silk and Wool on Relative Humidity and Moisture 

 Content.^ E. J. Murphy and A. C. Walker. The data reported 

 show that the resistivity of cotton is about 10'^ times greater at 

 1 per cent humidity than at 99 per cent, that it is an exponential 

 function of relative humidity in the range 20-80 per cent and a power 

 function of moisture content over the whole range investigated. By 

 means of the equations expressing these relationships the resistance of 

 a cotton sample can be calculated for any moisture content (or the 

 relative humidities corresponding to it) provided a measurement has 

 been made at a single moisture content. The curves for the logarithm 

 of resistance vs. relative humidity (or moisture content) for samples 

 of cotton containing different amounts of electrolytic material are 

 parallel, low electrolyte content corresponding to high resistance. 

 Similar but less extensive measurements were made on silk and wool. 



^ Journal of the Optical Society of America and Review of Scientific Instruments, 

 Vol. 17, December, 1928, pp. 428-434. 



' Joiiryial of the Optical Society of America and Review of Scientific Instruments, 

 Vol. 17, December, 1928, pp. 435-439. 



* Mining and Metallurgy, Vol. 9, November, 1928, pp. 483-486. 



^ Journal of Physical Chemistry, Vol. 32, December, 1928, pp. 1761-1786. 



