HEAT. 



307 



" Liberty Cap," 50 feet high and 20 feet in diameter ; and Fig. 136, on page 

 132, represents calcareous (travertine) terraces on this river. 



One of the geysers in the Upper Geyser Basin of the Fire-Hole is shown 

 in action in Fig. 283 ; the cone (Fig. 281) is but 3 ft. high and 5 in diameter, 

 but it throws up a jet beyond 200 ft. in height about once a day. 



In the eruption of a geyser, the jet is lirst 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. 



280. 



281. 



Giant Geyser. 



Beehive. 



282. 



Liberty Cap. 



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

 to hot rocks, producing steam, which seeks exit by conduits upw^ard ; (2) to 

 cooler superficial waters descending those conduits to where the steam pre- 

 vents 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 after an examina- 

 tion of the geysers of Iceland. The deposit of silica in the throat of the 

 conduit, after an eruption, tends to diminish its size, and sometimes closes it 

 completely, so that the waters are obliged to open a new vent. 



The beauty of the siliceous geyser-cones is often enhanced by the delicate tints of 

 pink, buff, yellow, etc., mingled with white, over their surfaces. Pebbles in the bottom 

 of the small basins formed about the cones are commonly concretions of geyserite, like 

 the rosettes of the bottom and sides. Fig. 280 represents the cone of the " Giant " geyser, 

 in the Upper Geyser Basin of the Fire-Hole ; it is about 10 feet high and 24 feet in di- 

 ameter at base, and has one side partly broken down and bent inward. It throws out, 

 at long intervals, a jet 90 to 200 feet in height. " Old Faithful " is one of the largest of 

 the Madison River geysers ; it has a low and broad irregular cone, and throws up its great 

 jet to a height of 150 feet, once in about 65 minutes, the remarkable regularity of its 

 action having suggested the name it bears. The " Giantess," another of the large geysers 

 of the Fire-Hole, throws a still larger body of water to the same height. Another, the 

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

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

 working together, and producing a marvelous effect from the ever-changing views. 



Frank H. Bradley observes that, while standing on the mound of " Fountain " geyser, 

 whose pool was overflowing, and watching a steam-jet a hundred yards away, the jets sud- 

 denly ceased, and " Fountain " commenced throwing np a jet, 10 feet in diameter, to vary- 



