106 



IGNEOUS AGENCIES. 



manner by deposits of the same, in the form of scalloped embroidery 

 set with pearly tubercles; in others the siliceous deposits take the 

 most fantastic forms (Figs. 85, 86, 87). In some places the silica is 

 deposited in large quantities, three or four inches deep, in a gelatinous 



condition like starch-paste. Trunks and 

 branches of trees immersed in these 

 waters are speedily petrified. 



We can only mention a few of the 

 grandest of these geysers : 



1. The " Grand Geyser," according to 

 Hayden, throws up a column 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 min- 

 utes. In a state of quiescence the tem- 

 perature of the water at the surface is 

 about 150°. 



2. The " Giantess " throws up a large 

 column twenty feet in diameter 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. Its erup- 

 tions are fitful but last sometimes several 

 hours. 



3. The "Giant" (Fig. 88) throws a 

 column five feet in diameter 140 feet 

 high, and plays continuously for three 

 hours. 



4. The " Bee - Hive " (Fig. 89), 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. 



Theories of Geyser-Eruption. — 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. 



Mackenzie's Theory. — 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. 



Fig. 90.— Forms of Geyser-Craters (after 

 Hayden). 



