ABSTRACTS OF TECHNICAL ARTICLES 629 



and to that extent allows a more accurate calculation of the identity 

 periods of the crystalline forms to be made. 



A partial transformation of the beta to the alpha form of gutta- 

 percha results by stretching at 80° C, although the exact conditions 

 under which this occurs have not been determined. 



The identity period in the fiber direction of the beta modification 

 is 4.77 ± 0.03 A., or double this value, and the alpha modification 

 presents an anomaly in that two identity periods are in best agreement 

 with the data. These are 9.00 ± 0.05 and 8.70 ± 0.13 A. In the 

 case of the beta modification three possible orthorhombic unit cells 

 which are in agreement with the observed lattice plane spacings are 

 given. 



Fields Caused by Remote Thmiderstorms.^ K. E. Gould. The 

 object of the studies described in this paper was to verify the sup- 

 position that certain types of short-duration longitudinal voltages 

 appearing in communication circuits are caused by remote thunder- 

 storms. By means of simultaneous directional measurements made in 

 the frequency range below 40 kilocycles at two points as much as 900 

 miles apart, thunderstorms at distances of several hundred miles from 

 one or both of these points have been located with a degree of accuracy 

 great enough to permit conclusive correlation of the storm locations 

 indicated by the directional measurements with the locations of 

 recorded thunderstorms. Methods, equipment, and results are 

 discussed. 



Improved Types of Transmission Measuring Systems and Methods 

 of Measurement.'^ W. H. Harden. The quantitative measurement 

 of the electrical efificiency of telephone circuits as one of the important 

 checks of the ability of these circuits to satisfactorily transmit speech 

 has become an increasingly important maintenance function during 

 the past twenty years. The function of transmission measuring 

 equipment is not only to provide a convenient tool for quickly checking 

 the electrical efficiency of telephone circuits, but also to serve as an 

 aid in locating the cause of trouble when it is found to exist. It is 

 the purpose of this paper to review briefly the progress which has been 

 made in transmission testing technique and to describe some recent 

 advances in the art which greatly facilitate this important part of 

 telephone maintenance work. The discussion of these advances in 

 the art will, we believe, be of interest to the railroads in connection 

 with the operation and maintenance of their private telephone systems. 



^Elec. Engg., June, 1936. 



*Proc. Assoc. Amer. Railroads — Telegraph and Telephone Section, June, 1935. 



