APPENDIX 271 



time I was stationed at Delagoa Bay, where the English, 

 Tembe, Umvelosi, and other rivers debouch. Thunder- 

 storms during the rainy season were of very frequent 

 occurrence. Durban, some 360 miles south, is situate at 

 the mouth of the Umgeni river, and in the same season is 

 visited by a thunderstorm almost every afternoon at about 

 the same hour. We are aware that such storms occur most 

 frequently within the tropics and diminish in frequency 

 towards the poles, during day rather than night, after 

 midday than before it, and in mountainous countries than 

 in plains, but we have no definite knowledge of the causes 

 which set up and set in motion the forces known to us as 

 natural earth-currents. 



Flammarion attributes the aurora borealis, which 

 sometimes illumines the darkness of night in the Arctic 

 and other regions of the North, to the striking of a balance, 

 silent and invisible, between two opposing tensions of 

 the atmosphere and the earth ; thus the apparition of the 

 aurora borealis in Sweden or Norway is accompanied by 

 electric currents moving through the earth to a distance 

 sufficiently great to cause the magnetic needle to record the 

 occurrence in the Paris Observatory . 



Indeed, the electricity which pervades the earth is 

 identical with that which moves in the heights of the 

 enveloping atmosphere, and whether it is positive or 

 negative its essential unity remains the same, these 

 qualities serving only to indicate a point, more or less in 

 common, between the different charges. The heights of 

 the atmosphere are more powerfully electrified than the 

 surface of the globe, and the degree of electricity increases 

 in the atmosphere with the distance from the earth. 



Atmospheric electricity undergoes, like warmth, and 

 like atmospheric pressure, a double fluctuation, yearly and 

 daily, as well as accidental fluctuations more considerable 

 than the daily ones. The maximum comes between six 



