T. A. Jaggar — Conditions affecting Geyser Eruption. 331 



atmospheric pressure at the reservoir-bottle with the stopper : 

 the same effect is produced by clamping the rubber supply tube 

 and thus checking the inflow of cooler water. When a power- 

 ful geyser-spring passes from an eruptive phase to quiescence, 

 or the reverse, there is probably a reflex effect on the level of 

 the source, for the total volumetric discharge is probably 

 usually less for the same period under thermal action alone, 

 than when hydrostatic pressure is combined with convection. 

 In other words, geyser eruption is probably not so effective a 

 method of drainage as continuous overflow in certain cases; 

 thus the eruptive phases of Excelsior may have induced a rise 

 of level in the source, an increase of head, and a consequent 

 return to a condition of violent overflow without eruption. 



4. Soaping Geysers. 



It has long been known that by artificially confining the 

 steam in smail-mouthed geysers of high surface temperature, 

 eruption may be brought about prematurely. In Iceland the 

 Strokr is thus stimulated by dumping into the neck of the 

 funnel large pieces of turf. In the Yellowstone district, it has 

 been found that a small amount of soap or lye added to the 

 geyser water will frequently hasten eruption. This is ex- 

 plained by Hague* as due to the increased viscosity of the 

 liquid. " Viscosity must tend to the retention of steam within 

 the basin and .... explosive liberation must follow .... 

 Viscosity in these hot springs must also tend to the formation 

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

 this in turn aids to bring about the explosive action, followed 

 by a relief of pressure, and thus to hasten the final and more 

 powerful display." Graham, f as a result of experiments with 

 an artificial geyser, agrees that viscosity has much to do with 

 the confinement of the steam, but questions the influence of 

 bubbles and foam. 



Experiment 3. The effect of soap. 



The apparatus was arranged to give regular eruptions as in 

 Experiment 1, with the geyser-tube flush with the bottom of 

 the basin and the water maintained about an inch deep in the 

 basin without overflow. A small quantity of fine shavings of 

 Ivory soap was thrown into the basin : these gradually dis- 

 solved and the milky solution was, after several eruptions, 

 sucked into the flask below. The occasional steam bubbles, 

 which, in pure water, rise rapidly through the geyser-tube and 



* Arnold Hague: Soaping Geysers, Trans. Amer. Inst. Min. Eug., vol. xvii, 

 1889, p. 546. 



f This Journal, January, 1893, p. 54. 



