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SCIENCE 



[N. S. Vol. XXXIII. No. 850 



quantities of these elements in the glassy 

 rhyolite through which these waters pass. 



The circulating ascending waters may, 

 to some extent, be charged by foreign sub- 

 stances other than by superheated aqueous 

 vapors. Nevertheless, in the park country 

 the vadose ascending waters do not appear 

 to have been greatly affected by any primi- 

 tive, deep-seated waters or their contents. 

 Even if foreign mineral matter were pres- 

 ent, it does not follow that the material 

 was not taken up originally by vadose 

 waters. 



In Iceland geological conditions are ap- 

 parently quite different, and volcanic 

 eruptions may be said, geologically speak- 

 ing, to be still going on, in strong contrast 

 to the Yellowstone Park, where such action 

 ceased many thousand years ago. In Ice- 

 land the thermal waters are, in my opin- 

 ion, mainly vadose, and their heat derived 

 from sources not far below the surface.^ 



I agree with Dr. Rudolf Delkeskamp" 

 that temperature, included gases, and sa- 

 linity in many localities are not in them- 

 selves conclusive evidence of the source of 

 thermal waters, and that far safer criteria 

 for the determination of the primitive 

 origin of waters are to be sought in uni- 

 formity of flow and chemical composition. 

 What I wish to emphasize, however, is that 

 the thermal waters of the Yellowstone Na- 

 tional Park are characterized by frequent 

 variations of temperature, progressive 

 transitions in chemical composition, lack 



* Since presenting this address I have received 

 from Dr. Thorkell Thorkelsson, of Copenhagen, a 

 copy of a suggestive paper on " I'he Hot Springs 

 of Iceland " which confirms me in the opinion of 

 the vadose origin of the Iceland thermal waters. 

 Dr. Thorlcell's paper appears as a recent publica- 

 tion forming one of the Memoir es de I'Academie 

 t Boyale des Sciences et des Lettres de Danemark, 

 Copenhague, 1910. 



' "Juvenile und vadose quellen," Balneologischen 

 Zeitung, XVI., Jahrgang, No. 5, 1905. 



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. 



RADIOACTIVITY OF THERMAL "WATERS 



Throughout this paper in the discussion 

 of the geological relations of the thermal 

 waters to the rhyolite eruptions laboratory 

 investigations bearing upon the composi- 

 tion of the rocks, waters, sediments and 

 gases have been utilized. In the discus- 

 sion 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 great measure 

 distinct from those treated here and time 

 does not permit of their consideration, and 

 in part because I know little about the 

 matter. My opinions are still open to con- 

 viction. With this avowal I may be al- 

 lowed to add that I am reluctant to be- 

 lieve that the source of the heated waters 

 is, geologically speaking, deep-seated or 

 sub-crustal. 



In this connection it might not be out of 

 place to mention the investigations of Pro- 

 fessor Herman Schlundt and R. B. Moore, 

 on the radioactivity of the thermal waters 

 of Yellowstone National Park, conducted 

 under the auspices of the U. S. Geological 

 Survey, and recently published.^" They 

 found the rhyolites, limestones, thermal 

 waters, gases, and sediments to be radioac- 

 tive. Specimens of rhyolite from widely 

 separated localities in the park were ex- 

 amined. These authors say: 



These data certainly seem to indicate that the 

 hydrothermal activity so manifest in the park is 



10 << ipjjg Eadioactivity of the Thermal Waters of 

 the Yellowstone National Park," U. S. Geol. Sur- 

 vey Bull., No. 395, 1909. 



