T. A. Jaggar — Conditions affecting Geyser Eruption, 333 



flow (hot springs) or spasmodic eruption (geysers). Both types, 

 as well as transitional forms, are represented in the Yellow- 

 stone Park. 



5. In general, those geysers which are irregular in their 

 eruptions have continuously overflowing vents ; and the most 

 regular geysers have confined waters, which overflow only dur- 

 ing eruption. This is explained by the fact that the overflow- 

 ing vents are under hydrostatic pressure, cooler water from 

 lateral ducts is continually replacing that which flows off, and 

 the ebullition necessary to produce eruption is thus prevented ; 

 eruption can only take place in the seasons of minimal inflow 

 of cooler water, when the heat is in excess. Where the water 

 is confined, on the other hand, and the supply of heat constant, 

 cooler water rushes in only after each eruption, and a definite 

 interval is required to bring it to the boiling point at the base 

 of the column. Overflowing and confined springs should be 

 distinguished in any description or classification of geysers. 



6. For the artificial stimulus of geyser eruption, an import- 

 ant effect of the bubble-forming alkalies, in small tubes, is the 

 initial depression of the water-column by the growth of a con- 

 fined cushion of minute steam bubbles. The release of pres- 

 sure induced by the final ejection of the froth column causes 

 eruption. 



