362 SCIENCE PROGRESS 



and dashes, which mingled with the intelligible signals and 

 confused their meaning. Now-a-days, by the use of a high- 

 spark frequency, the intelligible signals have a high shrill 

 note in the telephone and it is therefore possible to distinguish 

 them from the lower clicks, knocks or squeaks produced in the 

 telephone by the atmospherics. And, in addition, better forms 

 of tuning circuits have been devised for getting rid of the more 

 highly damped atmospherics. A study of these atmospherics 

 will undoubtedly lead to the increase of our knowledge of 

 atmospheric electricity ; indeed, a considerable amount of 

 information on this subject has already been accumulated. 

 Natural electric waves are produced whenever a lightning dis- 

 charge takes place, as this is just of a nature to produce a 

 sudden disturbance in the aether like the wave caused in the 

 air by an explosion. But as these stray waves are always found 

 flying across country, whether local thunderstorms are going 

 or not, there must be some constant source from which they 

 come ; it may well be that they arise in the tropical regions of 

 the earth and are propagated to temperate zones. On the other 

 hand, although stray electric waves can nearly always be heard 

 in the telephone of a radiotelegraphic receiver, in our latitude 

 they are much more frequent by night than by day ; moreover, 

 Mr. Marconi and Dr. Eccles have noticed that they undergo 

 a very curious stoppage or suspension just about sunset and 

 sunrise. The latter investigator has described the twilight 

 course of these stray electric waves in England in the following 

 terms : 



" Starting to listen (at the telephone) about a quarter of 

 an hour before sunset (in London) on a favourable afternoon 

 in late autumn or winter, the strays heard in the telephone are 

 few and feeble, as they have been all day ; then at five minutes 

 after sunset a change sets in, the strays slowly get fewer and 

 fewer until at ten minutes after sunset a sudden distinct lull 

 occurs and lasts perhaps a minute. Often, at this period, there 

 is a complete and impressive silence. Then the strays begin 

 to come again and quickly gain in number and force and in 

 the course of a few minutes they settle down into the steady 

 stream of strong strays proper to the night." 



In tropical countries great irregularities are noticeable but 

 broadly we may say that, at any place, these stray electric waves 

 are subject to regular diurnal variations something like those 

 of atmospheric electric potential or terrestrial magnetic force ; 



