I9II.] 



WHITEHEAD— HIGH VOLTAGE CORONA IN AIR. 



377 



charged electroscope. The initial discharge of the electroscope is 

 very sharply marked. Observations may be repeated at will and 

 after any interval ; when corrected for temperature and pressure a 

 most satisfactory constancy of results is obtained. Fig. i indicates 

 the essential parts of the apparatus. In the following a short de- 

 scription is given of the results of investigations of the influence of 

 the diameter of the conductor, of stranding the conductor, of the 

 alternating frequency, of wave form, of pressure, of moisture con- 



FiG. I. Arrangement of apparatus. 



tent and of temperature on the electric intensity at which atmos- 

 pheric air breaks down. The experiments on temperature, moisture 

 content and diameter of conductor are given in the paper mentioned 

 above. The results of the remaining investigations are first given 

 here. Xo attempt is made to describe the details of the experiments. 

 For these the reader may refer to the earlier paper and also to one 

 shortly to be presented to the American Institute of Electrical Engi- 

 neers in which the practical bearing of the results will be discussed. 

 Influence of Diameter of Conductor. — For convenience of refer- 

 ence a condensed table of the results on this portion of the work 



