PART II. POLAR MAGNETIC PHENOMENA AND TERRELLA EXPERIMENTS. CHAP. VI. 



673 



tit the radiation from Saturn would answer to 5 milliard kilowatts. This is comparatively no great amount 

 ( energy, for the lightning on our earth probably represents on an average from 4 to 5 milliard kilowatts. 

 This last figure I obtain in the following manner. 



AKRHENIUS computes the amount af combined nitrogen falling upon the land-surface of the earth 

 36 million sq. km.) in the form of nitrate and nitrite of ammonia, at about 400 million tons per annum, 

 we take for granted that a comparatively similar amount also falls upon the sea, this gives us one 

 rt out of every three million of the nitrogen of the atmosphere as the amount that is thus combined 

 ery year, and this, we may say with practical certainty, almost exclusively by electric discharge. 



Fig. a 5 8. 



Now as we know by experiment that by the most effective electric discharges 600 kg. of nitric 

 :id is formed by the air per kilowatt-year, we can calculate that the lightning that produces nitric acid 

 vpour in the atmosphere must at least answer to an average force-supply of 4 milliard kilowatts. 



We will return to our experiments with the large cathode-globe in our 32o-litre vacuum-box, as 

 t- as the previously-mentioned disruptive point-discharges are concerned, these, it will be remembered, 

 1 ing compared with sun-spots. 



It was soon evident that the quite smooth, silver-coated, large globe of 24 centimetres' diameter, 

 MS not by any means a success when it was a question of getting these negative point-discharges upon 

 i The smaller globes were much better, but it was apparent that the nature of their surface had much 

 t say in the matter. These experiments showed that with the smallest globe (2.5 cm. in diameter), it 

 MS easy to obtain, instead of the brief disruptive point-discharges, lengthy discharges from such points, 

 i ly provided there was a high vacuum, and that the current-strength of the discharge was great. These 

 {ncil-discharges would suddenly change place, and arrange themselves near the equator like the earlier 



