Apkil 14, 1911] 



SCIENCE 



567 



not connected with localized deposits of radiam. 

 In the above calculations the question of heat lost 

 by diffusion and other factors is not taken into 

 consideration, but after allowing a generous mar- 

 gin 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 eon- 

 tent of the rocks. 



Recently deposited travertine at the 

 Mammoth Hot Springs, as well as that of 

 the Main Terrace, and from the pre- 

 glacial capping on Terrace Mountain, was 

 subjected to similar tests. The same au- 

 thors 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 approxi- 

 mate time tliat has elapsed since the glacial period 

 in the park. 



Furthermore, a sample of the Jurassic 

 limestone underlying the Mammoth Hot 

 Springs proved to be more radioactive than 

 the most active sedimentary rocks tested 

 by that eminent authority, E. J. Strutt, of 

 England. It is noteworthy that the latter 

 rocks referred to were specimens of the 

 oolite formation from near the celebrated 

 springs of Bath. 



Strutt has also pointed out that siliceous 

 igneous rocks are more radioactive than 

 basic lavas,'^ a highly significant observa- 

 tion when it is borne in mind that the 

 rhyolite of the Yellowstone National Park 

 stands preeminent as an acid, crystalline 

 rock. Iddings and Cross^^ have shown 

 that allanite, in microscopic crystals, is 

 widely but sparsely distributed in the 

 siliceous igneous rocks of the Rocky Moun- 

 tains, and has been detected in the rhyolite 

 of Yellowstone National Park. Now 



" R. J. Strutt, " On the Distribution of Radium 

 in the Earth's Crust, and on the Earth's Internal 

 Heat," Proo. Roy Soc, Ser. A, Vol. LXXVII., 

 1906, p. 479. 



" Jos. P. Iddings and Whitman Cross, Am. 

 Jour. Sci., 3d ser.. Vol. 80, August, 1885, p. 108. 



allanite is known to carry small quantities 

 of thorium. It is a coincidence worthy of 

 note that thorium emanation was deter- 

 mined in several of the hot pools, it being 

 first observed in this country in thermal 

 waters in an obscure hot spring in Norris 

 Basin. I see no reason, however, to doubt 

 the conclusions of Messrs. Schlundt and 

 Moore that the heat produced by radio- 

 active emanations from the rocks and 

 waters is wholly inadequate to meet the 

 requirements. It seems necessary, at least 

 from our present knowledge, to look else- 

 where for the source of the heat dissipated 

 by the thermal waters of the Yellowstone 

 Park. 



SUMMARY 



In conclusion I may state that I have at- 

 tempted to show (1) that igneous activity 

 was continued throughout Tertiary time; 

 (2) that this activity came to an end with 

 the close of Pliocene time; (3) that during 

 the Eocene and Miocene deep-seated waters 

 were active geological agents, and that 

 these waters were essentially primitive in 

 their origin; (4) that in strong contrast to 

 the explosive, volcanic conditions of the 

 Miocene, the Pliocene lavas were emitted 

 under far quieter conditions and built up 

 the successive flows that formed the rhyo- 

 lite plateau; (5) that during the many 

 thousand years since the withdrawal of 

 glacial ice, the Pliocene rhyolites have, 

 since the beginning of Pleistocene time, 

 been steadily undergoing progressive 

 changes, brought about by the action of 

 enormous volumes of superheated vadose 

 waters; (6) that the gases contained in the 

 thermal waters were in great measure de- 

 rived from vadose sources; (7) that the 

 eruptions and periodicity of geysers are 

 phenomena due essentially to varying con- 

 ditions of reservoirs and channels of 

 superheated waters situated only short dis- 

 tances below the surface; (8) that the 



