320 



ATMOSPHERIC ELECTRICITY. 



the Antarctic where there is a permanent covering of snow and ice with that of ordinary 

 land and the open ocean. 



On the arbitrary scale used (approximately that defined by El.ster and Geitel and denoted 

 by A) * we found during our voyage the following results : — 



Tabi/E 161. 



Radio-activity. 



Exactly the same instruments and methods were used in the Antarctic with the following 

 results : — 



Table 162. 



Rculio-asiivity at Cape Evans. 



We see that the radio-activity in the Antarctic is higher than over the open ocean 

 and lower than over the land of South Africa. This is exactly what we should expect if 

 the origin of the emanation is the radium contained in the rocks of the earth's crust. 



AVhen the effect of the meteorological conditions are considered, we find here as in every 

 other part of the world that the meteorological conditions which favour stagnation of the air 

 near the ground result in relatively high radio-activity. Thus we should expect the radio- 

 activity to decrease with increasing wind force and to increase with decrease of temperature 

 and this is found to be the case. The mean values of the radio-activity for various wind 

 strengths and temperatures are shown in the following table : — 



Table 16.3. 



Rculio-activity. wind and temperature. 



* Elster and Geitel. Phys. Zeit., 1902, Volume 3, page 305. 



