420 



EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



/C'/ 





c 



whole lasting for several minutes.* The strata of water, being succes- 

 sively relieved of the pressure, rise and flash into the gaseous form, 

 one after the other, until the ebullition has descended from the middle 

 of the tube to a i)oint near the bottom. That there 

 was no motion, or scarcely any motion, below 

 while the violent eruption was taking place above 

 was i)roved by letting down to various depths 

 stones suspended on strings. Those sunk to points 

 near the bottom of the tube were undisturbed, 

 while those nearer the surface were cast out to 

 great heights. Bunsen even allowed his ther- 

 mometer to remain at the bottom of the tube and 

 it was undisturbed t during a great eruption, 

 which reached the height of 142 feet. 



Prof. J. H. J. Miiller, of Freiburg, constructed 

 an artificial geyser to demonstrate Bunsen's the- 

 ory. Fig. 29 represents an artificial geyser. If 

 an iron tube, A C, about G feet in length, is sur- 

 mounted by a basin and filled with water, when 

 heat is applied at two places, A and B, the phe- 

 nomena of a geyser eruption will be reproduced. 

 The heating at B is to represent the point of near- 

 est approach to the boiling point in the geyser- 

 tube, while the heat at A imitates the high tem- 

 perature at the bottom of the geyser. The differ- 

 ence, therefore, between the natural and the arti- 

 ficial geyser is that in the former the eiiect is not 

 necessarily due to two distinct sources of heat, as 

 the two fires A and B in the illustration, but is 

 caused by the continual influx of heat from the 

 bottom or side of the shaft. Although there is a 

 circulation of water in the tube, there is not an 

 equalization of the heat throughout it. This is 

 due in part to the impeding of the circulation by 

 the roughness of the walls, and partly because 

 the water is freed by long boiling from all mixture 

 of air, especially at the bottom of the geyser. 



Comstocli (in report of Captain Jones on North- 

 western Wyoming, p. 257) thinks Buusen's theory 

 has not yet been proven adequate to explain the 

 more i^rominent features of geyser eruptions. ISTor 

 does it, in his opinion, account for all the differ- 

 ences between geysers and hot springs, and he pro- 

 poses a structural hypothesis which combines Bis- 

 chof 's and Bun sen's theories. Fig. 30 is an illus- 

 tration taken from his report (p. 256), and is in- 

 tended to represent the supposed condition of the 

 subterranean geyser waters in the first stage of an 

 eruption. The reservoir d contains water, which 

 remains in equilibrium at the level shown in the 

 illustration. "By constant accessions of heat 

 Fig. 29.— Aitiflciai Geyser, from bclow, the vacant ijassage above is finally 

 filled with vapor, and by degrees the water in the bent passage h be- 



* Tlie description of the eruptions is given in Chapter I, Part II. 



tThe explanation of this curious fact will be given on a succeeding page. 



:b 



^ 



