SOAriNG GEYSERS. 159 



If soap or lye is tliiowii into most of the small pools, a viseous tluid 

 is formed; and viscosity is, I think, the piineipal cause in hastening 

 geyser action, Mscosity must tend to the retention of steam within 

 the basin, and, as in the case of the super-heated waters, where the 

 temperature stands at or above the boiling point, explosive liberation 

 must follow. All alkaline solutions, whether in the laboratory or in 

 nature, exhibit, by reason of this viscosity, a tendency to bump and 

 boil irregularly. Viscosity in these hot springs must also tend to tiie 

 formation of bubbles and foam when the steam rises to the surface, 

 and this in turn aids to bring about the explosive action, followed l)y a 

 relief of pressure, and thus to hasten the final and more powerful dis- 

 play. Of course relief of pressure of the superincumbent waters upon 

 the column of water below the surface basin is essential to all eruptive 

 action. These conditions, it seems to me, are purely physical. Un- 

 doubtedly the fatty substances contained in soap aid the alkali in ren- 

 dering the water viscous. On the other hand, when concentrated lye 

 is used it acts with greater eneigy and furnishes a viscous fluid, where 

 soap would yield only surface suds insufficient to accomplish any phe- 

 nomenal display. 



It is well known that saturated solutions of mineral substances 

 raise the boiling-point very considerably, the temperature having been 

 determined for many of the alkaline salts. Fn general, I believe the 

 boiling-point increases in proportion to the amount of salt held in solu- 

 tion. Actual tests have shown that the normal boiling-point of sili- 

 ceous waters in the Park does not differ appreciably fi'om the ordinary 

 surface waters, mainly, I suppose, because they are extremely dilute 

 solutions. 



The amount of lye required to produce a sufficiently viscous condi- 

 tion of the waters increases but slightly the percentage of mineral 

 matter held in solution. 



All the waters of the principal geyser basins ])resent the closest 

 resemblance in chemical composition, and, for the purposes of this 

 paper, may be considered as identical in their constituents. They have 

 a common origin, being, for the most jiart, surface waters which have 

 percolated downward for a sufficient distance to come in contact with 

 large volumes of steam ascending from still greatei- depths. The min- 

 eral contents of the hot s])rings are mainly derived from the acid lavas 

 of the Park plateau, as the resnlt of the action of the ascending steam 

 and sui»er-heated waters upon the rocks below. These thermal waters 

 are essentially siliceous alkaline water, carrying the same constituents 

 in somewhat varying (luantities, but always dilute solutions, ne\'er ex- 

 ceeding two grams of mineral matter per kilogram of water. When 

 cold they are potable waters, for the most part slightly alkaline to the 

 taste, and probably wholesome enough, unless taken daily for a long- 

 period of time. 



The following analyses of three geyser waters, sele<;ted from the 



