OBSERVATIONS OF ATMOSPHERIC ELECTRICITY. 333 



METEOROLOGY. 



The Importance of a General System of Simultaneous Observa- 

 tions of Atmos]pherie Electricity. 



BY W. E. AYRTON AND JOHN PERRY, 

 Professors in the Imperial College of Engineering, Tokio, Japan. 



The great practical value of simultaneous meteorological observations is 

 the assistance they afford us in enabling fairly accurate predictions of the 

 weather to be made some hours in advance. 



But all these observations are derived from instruments like the barom- 

 eter, thermometer, etc., which are only affected by the air or other bodies 

 in their immediate neighborhood- A disturbance produced in the higher 

 regions of the atmosphere cannot possibly affect the barometer or thermom- 

 eter until this wave of disturbance has traveled down to the lower air strata, 

 whereas electrical and magnetic instruments are instantaneously sensitive 

 to disturbances produced at great distances : the pneumatic desjiatch and 

 the electric telewraph may, in their difference of speeds, be taken as fairly 

 analogous with the sluggish barometer and ever-watchful electrometer. 



Dr. Veeder has drawn attention forcibly to the fact that even surface 

 winds, although they affect the weather, produce no change in the barom- 

 eter. 



JSTow, since the value of all storm warnings increases with the time by 

 which they precede the danger, the day may come when electrical and mag- 

 netic observations may not only aid, but actually supplant barometric 

 observations, 



Mr. Cromwell Yarley, the well-known electrician, having noticed that 

 on several occasions earth currents were followed by a change of weather, 

 communicated this fact to Admiral Fitzroy, who found such information so 

 much assistance to him in predicting the coming of storms, that he requested 

 to have it regularly supplied, "On some occasions," says Mr. Varley, "Ad-, 

 miral Fitzroy could see the ajjproach of a storm days before the barometer 

 indicated anything of the kind." 



Our present knowledge of this subject may be summed up nearly in the 

 words of Sir William Thomson in his address as president to the Society of 

 Telegraph Engineers. Suppose for a moment that there were no electricity 

 whatever in the air — that the air was absolutely devoid of all electric man- 

 ifestation, and tbat a charge of electricity were given to the whole earth. 



Well, now, if space were non-conducting — and experience on the vacuum 

 tubes seem rather to support the possibility of that being the correct view 

 — if all space were non-conducting, our atmosphere being a non-conductor, and 



