Boltwood — Radio-activity of Natural Waters. 387 



On applying these data to the occurrence of natural radio- 

 active waters, it would seem as if all the observed facts could 

 be readily explained. An extremely minute trace of uranium 

 minerals in the rocks and soil through which the waters perco- 

 late in their underground passage would be sufficient to impart 

 to them radio-active properties, which could be readily detected 

 by the sensitive method at command. It can be anticipated 

 that waters which rise through strata containing appreciable 

 quantities of uranium minerals will be found more highly 

 radio-active than any which have thus far been described. 

 The results obtained from the examination of waters from 

 springs in well-known uranium localities can be looked forward 

 to with interest. 



In those cases, at Bath and at Baden-Baden, where the 

 waters have been found to carry traces of radium in solu- 

 tion, it can safely be assumed that the decomposing action 

 of the waters due to their high temperature is still further 

 increased by the pressure and by the fact that they contain 

 various chemical substances in solution. These latter, while 

 they promote the decomposition of minerals, may also retard 

 the removal of the radium through the formation of insoluble 

 sulphates, phosphates, etc. The fact that these waters on reach- 

 ing the surface almost immediately deposit the greater portion 

 of their radium is indicative of the difficulty with which that 

 element is retained in solution. 



In view of the extraordinary sensitiveness of the radio-active 

 test for the radium emanation, it is very surprising that sam- 

 ples of gases from four of the springs examined by Curie and 

 Laborde were found by them to be quite inactive. 



139 Orange St., New Haven, Conn., 

 October 11, 1904. 



