
"Pant I. Sect.i.§2].. GEYSERS.  - 237 
the ground in certain tracts is honeycombed with passages which 
communicate with the surface by hundreds of openings, whence 
_ boiling water and steam are emitted. In most cases, the water remains 
- clear, tranquil, and of a deep green-blue tint, though many of the 
otherwise quiet pools are marked by patches of rapid ebullition. 
_ These pools lie on mounds or sheets of sinter, and are usually edged 
round with a raised rim of the same substance, often beautifully fretted 
and streaked with brilliant colours. The eruptive openings usually 
appear on small, low, conical elevations of sinter, from each of which 
one or more tubular projections rise. It is from these irregular tube- 
like excrescences that the eruptions take place. 
The term geyser is restricted to active openings whence columns 
of hot water and steam are from time to time ejected; the non- 
eruptive pools are only hot springs. A true geyser should thus 
possess an underground pipe or passage, terminating at the surface in 
an opening built round with deposits of sinter. . At more or less 
_ regular intervals rumblings and sharp detonations in the pipe are 
followed by an agitation of the water in the basin, and then by the 
violent expulsion of a column of water and steam to a considerable 
height inthe air. In the upper Fire-hole basin of the Yellowstone 
Park one of the geysers, named “Old Faithful” (Fig. 45), has ever 


















































































































































































































































































































































































































































































Fic, 45.—View oF OLD FalTHFUL GEYSER, AND OTHERS IN THE DISTANCE, 
Fire Hoxie River, YELLOWSTONE Park. 
‘since the discovery of the region, sent out a column of mingled water 
and steam every sixty-three minutes or thereabouts. The column rushes 
_ upwitha loud roar to a height of more than 100 feet, the whole eruption 
not occupying more than about five or six minutes. The other geysers 
of the same district are more capricious in their movements, and 
some of them more stupendous in the volume of their discharge. The 

