Badioactivity of Mineral Springs, 



151 



By examining in this way some of the most active materials, 

 I could see that each produced a certain amount of emanation, 

 the activity of which decayed with time at rates not very 

 dissimilar from that of radium emanation. 



Fijr. 2. 



TO EARTH 



The sediment of the Source d'Alun of Aix-les-Bains 

 produced considerable effects, the conductivity in the testing- 

 vessel rising to several hundred times the normal value. 

 After the introduction of the emanation into the testing- 

 vessel the conductivity increased steadily until it reached a 

 maximum, and then began to decay according to an expo- 

 nential law, falling to half its value in 3*2 days. 



The activity of the emanation obtained from this sediment 

 has, as one can see, a rate of decay somewhat more rapid 

 than should be expected for radium emanation, but the 

 result is in close agreement with the one obtained by Ebert 

 and Ewers with emanation contained in air removed from 

 the soil*. It also differs only slightly from the value given by 

 Adams for the rate of decay of emanation obtained from 

 Cambridge tap-water f. 



But a fact that struck me in the course of these measure- 

 ments was that some of the most active deposits, as for instance 

 those of Salins-Moutiers, when tested in the manner which I 

 have now described, seemed to produce a very small amount 

 of emanation as compared with the large amount obtained 

 from other sediments which appeared to be much less active 

 when examined by the method described in the first part of 

 this note. 



* Phys. Zeit. iv. p. 162 (1902). 

 t Phil. Ma-. Nov. 1903. 



