176 GEYSERS. 
the individual peculiarities of geysers, but such chambers do not form 
a vital, essential part of the geyser mechanism. 
In anexcellent résumé of the various theories of geyser action, Dr. 
A. ©. Peale states that he believes no one theory is adequate to explain 
all the phenomena of geyser action, though Bunsen’s theory comes 
nearest to it. * 
I believe however that Bunsen’s theory is a perfect explanation if 
we but admit that the geyser tube may be neither straight nor regular, 
but of any shape or size, and probably differing very much for each 
vent. The shape of the bowl or basin exercises but little influence upon 
the eruption save to produce the many individual peculiarities of the 
geyser column. 
Origin of Geysers.—It should be noted that Bunsen’s theory of geyser 
action is quite independent of his theory of geyser formation. The 
building up of a siliceous tube by the evaporation of the waters at the 
margin of a hot spring, is a process which may be seen in operation in 
any of the geyser regions of the world; but it is not a necessary pre- 
lude to the formation of a geyser, for a simple fissure in the rock 
answers equally well, as is shown at the Norris geyser basin in the 
Yellowstone Park. 
The life history of a geyser varies, of course, for each one, but obser- 
vations show that the following sequence of events often takes place. 
The hot vapors rising from unknown depths penetrate the rocks along 
planes of fracture and shrinkage cracks, decomposing and softening 
the rock until the pressure of the steam and water is sufficient to force 
an opening to the surface. If this opening affords an easier exit for 
waters issuing at a higher level the fissure is probably opened with a 
violent ejection of mud and débris; more often the process is a gradual 
one, accompanying the slow eating away of the rock walls along the 
fissure. The flowing waters slowly clear out the fissure, forming a tube 
that permits the freer escape of hot water and steam, while at the same 
time the waters change from a thick mud to a more or less clear fluid. 
The spring, at first a simple boiling mud-hole, is now an intermittently 
boiling spring, which soon develops true geyser action. If the open- 
ing of the fissure afforded a new outlet for the waters of some already 
existing geyser, these changes take place rapidly, and eruptions begin 
as soon as the pipe is sufficiently cleared to hold enough water. The 
bare rock about the vent or fissure is soon whitened by silica deposited 
by the hot waters. This sinter may form a mound about the expanded 
tube or basin, or, if the vent be small and spray is frequently ejected, 
it builds up the curious geyser cones so prominent in the Yellowstone. 
In certain cases the building up of these deposits may partially choke 
the geyser’s throat, and cause a diminution of the geyser’s energy, 
whose forces seek an easier outlet. In other cases the eating out of 
new subterranean waterways deprives the geyser of its supply of heat, 
*Twelfth Ann, Rept, U, S, Geol. and Geog, Survey Territories, vol. 11., p. 422. 
