oll 
fall towards low values and then a rather sudden rise. An increase in flow 
is accompanied by an increase in radioactivity. 
The increase of flow follows the melting of a heavy snow or a heavy rain. 
Thus the radioactivity of the spring depends upon the rain fall. The radio- 
activity of rain water is very small compared to the values obtained at the 
springs. It can not be due to the radioactivity of rain water. 
The above results, together with the fact that ““wet weather” springs are 
very radioactive and that one on the campus of Indiana University measured 
1920 x10-" a short time after a heavy rain fall, lead to the conclusion that the 
variation of the emanation content of Indiana springs is due to the rain water 
percolating through the soil and dissolving and carrying down with it some 
of the emanation which is continually moving upwards from the interior of 
the earth to the surface. During dry weather when the flow of the water is 
not rapid a large per cent of the emanation which was dissolved in the water 
is transformed into radium A, B, C, and D before the water issues from the 
ground. 
This conclusion is in accord with the observations of Wright & Smith 
(Phys. Rey. Vol. 5, p. 459, 1915) in which they find that the amount of 
emanation which issues from the soil is decreased as much as 50 per cent at 
times after heavy rains. 
To recapitulate, the variation of the emanation content of spring water is 
due to the rain water dissolving emanation as it percolates through the soil. 
Department of Physics, Indiana University, December 1, 1915. 
TABLE I. 
Variation of the Emanation Content of Certain Springs near Bloomington 
Indiana. (Flow given in gallons per day.) 
Horrie SPRING. ILLINOIS CENTRAL SPRING. 
Temp Tee Temp.| Flow. Oa 
DA C. Riga C anes C. G ures 
o per Liter. y per Liter. 
1914 
Sent ake.’ si2>: yen | 650x10-! | 445x10-" 
Oictre a: LON. 8.0 13 695 12.8 166 
(ene Se eern sek 13.3 700 13 120 
Octean O04 =. 22. 13 10000 665 | 12.7 | 130000 20 
Nov. Ore na: 13 650 12.6 40 
