364 RADIO-ACTIVITY OF THE ATMOSPHERE [CH. 
due to the emanation from fango, with that due to the radium 
emanation, and within the limit of error, the decay curves obtained 
were found to be identical. There can thus be little doubt that 
the activity observed in fango is due to the presence of a small 
quantity of radium. Elster and Geitel calculate that the amount 
of radium, contained in it, is only about one thousandth of the 
amount to be obtained from an equal weight of pitchblende from 
Joachimstahl. 
The natural carbonic acid arising from great depths of old 
voleanic soil was also tested. The carbon dioxide was obtained 
from the works in the liquid state. The gas was found to show 
distinct activity, and was able to produce excited activity on the 
surface of the vessel. After an interval of 16 days the gas was 
again tested and found to be inactive. 
These results are similar to those of J. J. Thomson, who found 
an active emanation in the water obtained from deep wells. 
214. Effect of meteorological conditions upon the 
radio-activity of the atmosphere. The original experiments 
of Elster and Geitel on the excited radio-activity derived from 
the atmosphere were repeated by Rutherford and Allan? in 
Canada. It was found that a large amount of excited radio- 
activity could be derived from the air, and that the effects were 
similar to those observed by Elster and Geitel in Germany. This 
was the case even on the coldest day in winter, when the ground 
was covered deeply with snow and the wind was blowing from the. 
north over snow-covered lands. The results showed that the 
radio-activity present in the air was not much affected by the 
presence of moisture, for the air during a Canadian winter is 
extremely dry. The greatest amount of excited activity on a 
negatively charged wire was obtained in a strong wind. In some 
cases the amount produced for a given time of exposure was ten 
to twenty times the normal amount. A cold bright day of winter 
usually gave more effect than a warm dull day in summer. 
Elster and Geitel* have made a detailed examination of the 
effect of meteorological conditions on the amount of excited radio- 
activity to be derived from the atmosphere. For this purpose a 
i Phil. Mag. Dee. 1902. 2 Phys. Zeit. 4, pp. 137, 138. 1902. 

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