HOT SPRINGS AND GEYSERS. 721 



great jet to a height of one hundred and thirty feet, once in about sixty five minutes, 

 the remarkable regularity of its action having suggested the name it bears. The 

 "Giantess " is another of the large geysers of the Fire-hole; the basin has a breadth 

 of twenty-three and a half by thirty -two and a half feet, and holds sixty-three feet in 

 depth of water, and at intervals throws the whole to a height of sixty feet. Another, 

 the "Architectural" geyser, is actually, when in action, a combination of jets of all 

 sizes and angles of inclination, each having some independence in its movements, but 

 all working together, and hence producing a marvellous effect from the ever-changing 

 views. 



Frank H. Bradley, of the expedition under F. V. Hayden, in 1872, observes that, 

 while standing on the mound of "Fountain " geyser, whose pool was overflowing, and 

 watching a steam-jet of a hundred yards away, the jets suddenly ceased, and "Foun- 

 tain " commenced, throwing up a jet, ten feet in diameter, to varying heights, from 

 five to forty feet. In thirty minutes, " Fountain " stopped suddenly, and immediately 

 the steam-jet began again ; in twenty minutes more, the jet again stopped, and at once 

 a small pool, a few yards from " Fountain," which was empty when that was playing, 

 but had become partly filled from its overflow, began to boil and throw up water 

 to a height of five or ten feet, and continued this for half an hour; as it moderated, 

 the steam-jet opened anew, but ceased when the boiling became more violent. The 

 facts prove a sympathy between different vents; and the same was illustrated in other 

 parts of the region. 



Bradley also states that, during the eruption of some of the larger geysers, there 

 are pulsating sounds or thumps, in the depths of the geyser conduit, which have no 

 parallel movement in the jet; and that, in an eruption of the " Giantess," there were 

 seventy-three of these pulsations a minute; and in that of "Grand" geyser, at first 

 seventy-two or seventy-three, but in the course of twenty minutes they decreased to 

 seventy, and became gradually fainter. 



These and other geysers, and additional hot-spring phenomena, are described in the 

 Reports of the expedition under Hayden, for the years 1871 and 1872. 



The siliceous geyser-cones are all beautiful concretionary work ; and the beauty of 

 form and texture and pearly lustre is often greatly enhanced by the delicate shades 

 of pink, buff, yellow, and other tints, mingled with white, over their surfaces. 

 Pebbles, in the bottom of the small basins formed about the cones, are commonly con- 

 cretions of the opal, like the rosettes of the bottom and sides. 



In the eruption of a geyser, the jet is first water; then much steam with the water; 

 and, at last, mostly or wholly steam, the water having been all thrown out; and, when 

 the water partly falls or runs back into the basin, the eruption is sometimes renewed 

 successively, before finally stopping. 



The action of geysers is owing (1) to the access of subterranean 

 waters to hot rocks, producing steam, which seeks exit by conduits 

 upward ; (2) to cooler superficial waters descending those conduits to 

 where the steam prevents farther descent, and gradually accumulating, 

 until the conduit is filled to the top ; (3) to the heating up of these 

 upper waters, by the steam from below, to near the boiling point ; 

 when (4) the lower portion of these upper waters becomes converted 

 into steam, and the jet of water or eruption ensues. This is nearly 

 the explanation given by Bunsen. The deposit of silica in the throat 

 of the conduit, after an eruption, tends to diminish its size, and some- 

 times closes it completely, so that the waters are obliged to open a 

 new vent. 



Hot springs also occur at many other points in, and* west of, the 

 Rocky Mountains. There is a region of springs of hot water and 

 46 



