812 BELL SYSTEM TECHNICAL JOURNAL 



electric vector in the plane of incidence. The distribution curves are 

 all perfectly symmetrical about the normal to the surface, showing 

 no tendency to follow the direction of the electric vector. 



Oscillographic Observations on the Direction of Propagation and Fading 

 of Short Waves.^^ H. T. Friis. The short-wave transmission path is 

 generally but not always located in the vertical plane through the 

 transmission and receiving points. 



Direction finding depends upon determining the direction of the 

 wave at the receiving point; it does not give accurate results when the 

 twilight zone is in the w^ay of the wave path. 



The angle between the earth and the direction of short-wave propa- 

 gation varies continuously and the changes in this angle are much 

 larger than the changes in angle of propagation in the horizontal plane. 



The observations are consistent with the view that the fading is 

 mainly caused by wave interference. 



An Improved Permeameter for Testing Magnet Steel}^ B. J. Babbitt. 

 The increasing use of cobalt steel in the manufacture of permanent 

 magnets has created a need for a permeameter that is capable of deter- 

 mining accurately the magnetic properties of such steel in bar form. 

 The common commercial permeameters are not capable of producing 

 the high magnetizing forces required for this purpose. Commercial 

 permeameters are chiefly of two types, the yoke type and the Burrows 

 type. The latter is difficult to operate and requires an experienced 

 operator for a reasonable output ; it cannot be adapted to the testing 

 of cobalt steel unless it is practically rebuilt throughout. The yoke 

 type of permeameter may be adapted to the testing of cobalt steel by 

 the use of extensions to the poles so that the distance between them 

 is much less. In this way the greater part of the magnetomotive force 

 is distributed over a short portion of the magnetic circuit and the mag- 

 netomotive force per centimeter is correspondingly greater. The 

 permeameter that is described below has been developed by the Mag- 

 netic Materials Division at the Hawthorne Works of the Western 

 Electric Company to overcome the chief objections common to present 

 commercial permeameters. 



Corrosion of Cable Sheath in Creosoted Wood Conduit}^ R. M. Burns 

 and B. A. Freed. This paper deals with the identification of a cor- 

 rosion of lead cable placed in creosoted wood conduit, and with the 



^^Proceedings of the Institute oj Radio Engineers, May, 1928, Vol. 16, No. 5, pp, 

 658-665. 



" Journal of the Optical Society of America and Review of Scientific Instruments 

 Vol. 17, No. 1, pp. 47-58, July, 1928. 



18 Journal of t lie A. I. E. E., Vol. XLVII, No. 8, pp. 576-579, August, 1928. 



