1902.] 



On Electric Earth-car rent Disturbances. 



225 



" Characteristics of Electric Earth-current Disturbances, and their 

 Origin." By J. E. Taylok. Communicated by Sir Oliver 

 Lodge, F.E.S. Eeceived December 16, 1902, — Eead January 

 22, 1903. 



The following notes refer to effects which appear to have a distinct 

 connection with the so-called " ionisation " of the upper regions of the 

 atmosphere by radiations from the sun, and which have repeatedly 

 attracted my attention during the course of recent experiments in 

 wireless telegraphy for the British Postal Telegraphs. 



In the electronic theory of the causes producing the aurora borealis, 

 it is assumed that by the deflection of the course of the flying ions or 

 electrons towards the poles, due to the earth's magnetic field, a con- 

 centration results in those neighbourhoods, giving rise to the pheno- 

 menon. 



The effects classed by telegraph engineers as earth-currents have also, 

 apparently, a direct connection with the ionisation of the atmosphere. 

 As is well known, these are at times, particularly when auroral displays 

 are in evidence, so strongly pronounced as to interfere more or less 

 with ordinary telegraphic working on earthed circuits. 



In special cases, where sensitive apparatus is used, they are, every 

 day, sufficiently pronounced to cause disturbance, for some hours at 

 least, even under normal conditions. They have been found to be 

 particularly troublesome in the Post-office system of wireless telegraphy, 

 in which a sensitive telephone receiver is connected in a low resistance 

 circuit earthed in the sea at both ends. 



To enumerate in a systematic manner the various investigations 

 which have been made from time to time on the subject of earth- 

 currents would involve a lengthy paper ; but only the more prominent 

 features which have forced themselves on my observation will here be 

 briefly summarised. 



The disturbances evidence themselves by producing various charac- 

 teristic noises in the telephone receiver. They have not been con- 

 founded with ordinary telegraphic or other inductive disturbances, 

 as they appear in circuits far removed from any such source of 

 affection. In these latitudes they are always stronger and of more 

 frequent occurrence in summer than in winter. They are daily in 

 evidence for a few hours at or about the time of sunset, i.e., whilst 

 daylight is fading. 



In general they do not evidence themselves to any great extent 

 during broad daylight, but are readily precipitated by atmospheric 

 electrical effects or any tendency to thunderstorms, and rarely, if 

 ever, fail to herald the approach of a storm or gale. 



