RADIOACTIVITY OF THERMAL WATERS 121 



terized by frequent variations of temperature, progressive transitions in 

 chemical composition, lack of uniformity in mode of occurrence, and 

 shifting in points of discharge; in other words, they lack the essential 

 characters of primitive waters derived from deep-seated sources. 



EaDIOACTIVITY of THERMAL WATERS 



Throughout this paper in the discussion of the geological relations of 

 the thermal waters to the rhyolite eruptions laboratory investigations 

 bearing on the composition of the rocks, waters, sediments, and gases 

 have been utilized. In the discussion of the circulation of descending 

 and ascending waters almost nothing has been said in relation to the 

 source of heat which raised the temperature of these waters. This is in 

 part due to the fact that the problems involved are in a great measure 

 distinct from those treated here, and time does not permit of their con- 

 sideration, and in part because I know little about the matter. My opin- 

 ions are still open to conviction. With this avowal I may be allowed to 

 add that I am reluctant to believe that the source of the heated waters is, 

 geologically speaking, deep seated or subcrustal. 



In this connection it might not be out of place to mention the investi- 

 gations of Prof. Herman Schlundt and E. B. Moore on the radioactivity 

 of the thermal waters of Yellowstone National Park, conducted under 

 the auspices of the United States Geological Survey and recently pub- 

 lished.^^ They found the rhyolites, limestones, thermal waters, gases, and 

 sediments to be radioactive. Specimens of rhyolite from widely separated 

 localities in the park were examined. These authors say : 



"These data certainly seem to indicate that the hydro-thermal activity so 

 manifest in the park is not connected with localized deposits of radium. In 

 the above calculations the question of heat lost by diffusion and other factors 

 is not taken into consideration, but after allowing a generous margin for error 

 we do not see how more than one per cent of the heat required for the hydro- 

 thermal action can be ascribed to the radium content of the rocks." 



Eecently deposited travertine at the Mammoth Hot Springs, as well as 

 that of the Main Terrace and from the preglacial capping on Terrace 

 Mountain, was subjected to similar tests. The same authors say: 



"The travertine of Terrace Mountain is overlain by glacial boulders. Since 

 its activity is only one per cent of the recent deposits, its age is about 20,000 

 years, which would also be the approximate time that has elapsed since the 

 glacial period in the park." 



Furthermore, a sample of the Jurassic limestone underlying the Mam- 

 moth Hot Springs proved to be more radioactive than the most active 



"The radioactivity of the thermal waters of the Yellowstone National Park. U. S. 

 Geological Survey Bulletin, 1909, p. 395. 



IX— Bull. Geol. Soc. A.m., Vol. 22, 1010 



