492 Elster and Geitel Electrical Dissipation Apparatus. 



as we have just seen, is least decisive. If London smoke is 

 the realty effective influence, then the effect should be con- 

 siderably dependent on the hour of the day, and when most 

 marked at Kew should be least marked at a station to the 

 east of London. A comparison of simultaneous results from 

 Kew and such a station should be decisive. If the low value 

 of the dissipation and the high value of the potential gradient 

 at Kew arise from its proximity to London, then the electrical 

 conditions in the heart of London itself are presumably highly 

 abnormal, and it seems unlikely that great abnormality in 

 any atmospheric condition will be without some influence on 

 living objects exposed to it. 



§ 14. B. Zolss has described a remarkable parallelism 

 between dissipation and the size of the daily range of 

 declination at Kremsmunster, and has explained this as a case 

 of cause and effect, dissipation representing a vertical electric 

 current, and declination cbange the consequent effect on the 

 magnetic needle. If such a connexion could be definitely 

 established, it would be a result of great physical importance. 

 Zolss' conclusions are given without criticism in Mache and 

 v. Schweidler's textbook of Atmospheric Electricity, and it 

 thus appeared worth while seeing whether any confirmation 

 was derivable from Kew results. One point deserving 

 attention is that the dissipation observations at Kew covered 

 only two hours, while the declination range represents mag- 

 netic changes during a larger fraction of the day. 



The diurnal range of declination, as Zolss himself recoo- 

 nized, agrees with dissipation in being considerably larger in 

 summer than in winter. If the two phenomena are compared 

 in a way which does not eliminate annual variation, then a 

 conclusion similar to Zolss' is practically certain to be reached. 

 But when the effects of annual variation are eliminated by 

 subdividing the observations of each month into two equal 

 groups composed respectively of the days of largest and of 

 least declination range, the Kew results at least afford no 

 support to Zolss' conclusions. It appeared sufficient to con- 

 sider one year, 1908. The final means derived from the 

 12 pairs of monthly groups were as follows : — 



Groups. 



Mean value of 



Declination .. n 

 Eange. *<«++«-* 



P. 



Days of largest declination range ... 

 ,, least ., ,, 



17 ! 6 

 9'2 



•540 

 •581 



210 



216 



