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THE POPULAR SCIENCE MONTHLY. 



umn of water six feet in diameter to the height of 200 feet, while the 

 steam ascends 1,000 feet or more. The eruption is repeated every 

 thirty-two hours, and lasts twenty minutes. In a state of quiescence 

 the temperature of the water at the surface is about 150. 



2. The " Giantess " throws up a large column twenty feet in di- 

 ameter to a height of sixty feet, and through this great mass it shoots 

 up five or six lesser jets to a height of 250 feet. It erupts about once 

 in every eleven hours, and plays twenty minutes. 



3. The " Giant " (Fig. 4) throws a column five feet in diameter 

 140 feet high, and plays continuously for three hours. 



4. The " Beehive " (Fig. 5), so called from the shape of its 

 mound, shoots up a splendid column two or three feet in diameter to 

 the height by measurement of 219 feet, and plays fifteen minutes. 



5. " Old Faithful," so called from the frequency and regularity of 

 its eruptions, throws up a column six feet in diameter to the height 

 of 100 to 150 feet regularly every hour, and plays each time fifteen 

 minutes. 



Fig. 6. Forms of Geysek-Cratehs (after Haydeu). 



The water of geysers is not volcanic water, but simple spring- 

 water. A geyser is not, therefore, a volcano ejecting water, but a 

 true spring. There has been much speculation concerning the cause 

 of their truly wonderful eruptions. 



According to Mackenzie, the eruptions of the Great Geyser may 

 be accounted for by supposing its pipe connected by a narrow conduit 

 with the lower part of a subterranean cave, whose walls are heated 

 by the near vicinity of volcanic fires. Fig. 1 represents a section 

 through the basin, tube, and supposed cave. Now, if meteoric water 

 should run into the cave through fissures more rapidly than it can 



