324: T. A. Jaggar — Conditions affecting Geyser Eruption. 



The accuracy of Bud sen's theory was early confirmed by 

 experiment and the only mechanism necessary to produce 

 geyser eruption is a tube filled with water, open above and 

 heated below. Many further experiments ^ have been made, 

 however, with a view to explaining the variations observed in 

 the period and interval of geyser eruptions, the relative amount 

 of steam and water, and the effect of artificial stimulants in 

 hastening eruption. Andrese's experiments were directed 

 toward the imitation of Peale's* types, a classification based on 

 the form of the basins and the relation of the periods of steam 

 and water in the eruption. It is noteworthy that in most of 

 these experiments, the apparatus recommended has an open 

 basin above, which retains the water thrown out and permits it 

 \oflow hack into the geyser tube. 



In Peale's classification no mention is made of the nature of 

 the geyser-spring during the interval of quiescence ; in some 

 cases there is continuous overflow or discharge, in others there 

 is no overflow except during eruption. As it may be shown 

 that this fact of the presence or absence of hydrostatic pressure 

 at the geyser vent has an important bearing on the conditions 

 of eruption, the writer would suggest a classification based on 

 this very simple distinction ; it is a singular fact that in the 

 published descriptions of geysers this point has been frequently 

 overlooked. If geyser waters represent meteoric drainage, 

 they are affected by the laws of hydrostatic equilibrium. In 

 such case a tube continuously overflowing is in a distinctly dif- 

 ferent class from one which throws off its waters to join the 

 superficial drainage to the sea only during the period of its 

 occasional or intermittent discharge. The first case is repre- 

 sented by such a geyser spring as " Excelsior," in the Yellow- 

 stone Park, a violently boiling cauldron in the hill slope, 

 continually discharging vast volumes of water into the pond 

 below, which in turn drains into the Firehole River; the 

 Great Geyser of Iceland and the Rotomahana Geyserf of New 

 Zealand are other types of the continually overflowing class. 

 " Old Faithful " is the type of the second class : its waters may 

 be seen in violent ebullition a few feet below the orifice of the 

 vent, but overflow takes place only during eruption. 



Any apparatus designed to imitate accurately either of these 

 must be provided with a supply reservoir having subterranean 

 connection with the geyser tube, by which water may siphon in 

 to replace that discharged. Obviously this replacement takes 

 place in nature: if the water, as asserted, is meteoric, and 

 governed by the same laws that determine the loci of springs, 

 the natural method of such replacement is by the action of 

 gravity. In the case of Excelsior, this subterranean compensa- 



* U. S Geological Survey of the Territories, 1884, vol. xii, pt. 2. 

 f Destroyed by the Tarawera eruption in 1886. 



