154 



Radioactivity of Mineral Springs. 



Fijr. 4. 



90 

 80 

 70 

 GO 



50 



k 



S 40 



k 



30 



ao 



10 



o 









! 





























































































































































































20 30 



40 



50 



Conclusion. 



The results given above show that besides the activity and 

 emanation probably due to traces of radium which several 

 physicists have observed in the sediments of a great number 

 of mineral and thermal springs, some deposits contain a 

 radioactive constituent, in all probability thorium, the emana- 

 tion of which loses half of its activity in about one minute, 

 and is capable of producing excited activity that decays with 

 time, falling to half its value in about eleven hours. 



I may add that attempts are now being made with the object 

 of separating by chemical means the radioactive constituents 

 and of determining as exactly as possible the amount of each 

 present in the different sediments. 



In conclusion I desire to express my heartiest thanks to 

 Lord Kelvin, w r ho was good enough to take some interest in 

 the present research, and did me the honour of witnessing 

 some of my experiments. 



