Emanation in the Lower Regions of the Atmosphere, 31 



Flemming*, and others. Gockel confirmed the conclusions 

 of Brandes, namely, when the barometer is low there is more 

 active deposit on a wire, and says that rain and gusty weather 

 produce an increase in the amount of emanation. In an 

 earlier paper he says there was more active deposit on fine days 

 than on wet ones. Kohlrausch, working in Vienna on the 

 radioactive induction, found that clouds had a considerable 

 effect, and that there was a decrease after rain and with 

 falling pressure; whereas Schvveidler found an increase in the 

 atmospheric ionization on stormy days. Amaduzzi supports 

 Ebert's contention that a fall of the barometer causes an 

 increase in the amount of emanation in the air. Constanzo 

 measured the active deposit over the Mediterranean and 

 found it increased when the wind blew from the land. 

 Some of the best work has been done by Simpson, who 

 carried out a long series of experiments in Lapland in 1905 

 on the active deposit from atmospheric radioactivity. He 

 found that 



(1) On the whole year temperature has a marked effect, 



but little effect during any one month ; 



(2) The radioactivity increases as the humidity increases 



and decreases as the humidity decreases ; 



(3) The radioactivity decreases as the wind increases in 



strength ; 



(4) The radioactivity is greater with a falling barometer 



than with a rising barometer, but the radioactivitv 

 is not necessarily higher with a low barometer than 

 with a high one ; 



(5) The radioactivity is greater with winds from the land 



than with winds from the sea. (In Lapland the 

 winds from the land are South winds, and occur when 

 the barometer falls. The winds from the sea are 

 North winds, and occur when the barometer rises.) 

 The wind effect was due to the barometer effect and 

 not vice versa. 



(6) There is no connexion with the amount of cloud and 



the radioactivity. 



(7) There is no relation between the radioactivity and the 



potential gradient. 



Simpson concluded by saying that all his work supports 

 Elster and GeiteFs view that when the atmospheric pressure 

 falls the emanation is sucked out of the ground. He also 

 found that everything which reduces the atmospheric circu- 

 lation increases the atmospheric radioactivity. 

 * Phys. Zeitsckr. Nov. 1908. 



