564 



SCIENCE 



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



springs in the three principal geyser 

 basins was any hydrogen sulphide detected. 



Professor Phillips says: 



There is, in fact, a curious gradation between 

 analyses from No. 1 and No. 10, as regards the 

 proportion of nitrogen and carbon dioxide. Oxy- 

 gen is present in all of them, and as ten of these 

 gases contain combustible elements, hydrogen and 

 methane, it is evident that the gas as it escapes 

 from the spring has not been exposed to a high 

 temperature. 



It is admitted by most authors that 

 under certain conditions all these gases 

 may be contained in surface waters. I 

 think it has been shown that under the 

 peculiar conditions in which these waters 

 occur, and their lack of uniformity of com- 

 position, they must be considered as ab- 

 sorbed by vadose waters. 



One of the most marked characteristics 

 and one of geological significance is the fre- 

 quent variation shown in temperature, 

 flow, and salinity of the thermal waters 

 where they issue from the rhyolite plateau. 

 The solvent power of water holding min- 

 eral matter in solution is, as is well known, 

 far greater than that of pure water. Now 

 the downward percolating waters gather 

 material from the disintegrated rhyolite 

 soil and in some measure from the soluble 

 salts previously brought up from below. 

 There is also a certain amount of carbon 

 dioxide derived from the atmosphere. It 

 is a fair assumption, therefore, that in 

 percolating downwards the waters carry 

 with them to the water level below no in- 

 considerable amount of material. 



The ascending superheated waters, under 

 pressiire, exert a far greater influence. 

 The work done by these waters, and that 

 which is still going on, is self-evident even 

 to the most casual tourist. It is shown by 

 the broad areas and ridges of altered and 

 bleached rhyolite. Nowhere is this more 

 in evidence than in the escarpments along 

 the Grand Canyon of the Yellowstone, 



where the gorgeous coloring is due to the 

 oxidation of the ferruginous minerals. The 

 potent influence of such waters under ex- 

 isting conditions can hardly be questioned. 

 They readily attack both the glassy ground- 

 mass and crystalline feldspars of the rhyo- 

 lite, and when the metasomatic changes 

 are complete they leave behind an impure 

 kaolinized material mixed with quartz and 

 held together by colloidal silica. 



DEVELOPMENT OF SPRINGS AND GEYSERS 



The ascending waters, in their circuitous 

 course, penetrate fresh seams and cracks 

 in unaltered rock which slowly widen 

 under the disintegrating influences of 

 aqueous vapors. Finally, the thermal 

 waters, following these cracks, issue at the 

 surface as hot springs and pools. The 

 early waters are usually acid in composi- 

 tion, and deposit ferric and aluminous 

 salts. Occasionally they set free sulphur, 

 derived from the decomposition of hydro- 

 gen sulphide. In time the openings 

 through which they flow become broader, 

 the waters themselves, free from hydrogen 

 sulphide, become clearer and neutral, and 

 ■ at last issue as siliceous alkaline waters. 

 Underground reservoirs are excavated and 

 become sources of hot springs, and, under 

 favorable conditions, geysers. The geyser 

 itself is simply a stage in the development 

 of geological processes. In time geysers 

 themselves become extinct. New geysers 

 break out and, given the essential physical 

 conditions, may develop eruptions quite 

 as flne as any in action at the present time. 

 Geologically speaking, the final stage of 

 thermal activity is a hot spring. The 

 tendency of a geyser is to develop a hot 

 surface pool. If from such pools there is 

 discharged a sufficient amount of overflow, 

 and if from the surface of these geyser 

 pools there is an ample dissipation of heat 

 into the surrounding atmosphere, explosive 



