THE MECHANICS OF INTERMITTENT SPRINGS. 375 



of the tube R, and fail to prevent the temperature of the whole water- 

 column from finally rising under the influence of the constant flow of 

 superheated water from the streams, W. The strata of water in the 

 middle of the tube finally reach the temperature of the boiling-point 

 at that depth. This water is then converted into steam, and thereby 

 the pressure upon the lower strata is diminished. Then the strata of 

 water still deeper in the tube are also converted into steam, and this 

 throws the masses of water above it energetically out of the geyser- 

 tube. The water being cooled somewhat in the air, a part of it 

 falls back in the tube, and, producing a reduction of temperature, 

 causes a short interruption of the formation of steam, but that is re- 

 sumed again as the superheated water flows in, and continues till the 

 whole column has been so reduced in temperature, by the water that 

 falls back, that the liquid strata no longer reach the boiling-point 

 corresponding with the pressure upon them, and the eruption ceases. 



According to the theory of Lang, the Great Geyser occupies a space 

 in the interior of the earth in shape somewhat like Fig. 3. The tube 



Fig. 3. 



R, by which the waters are connected with the surface, is bent upward 

 at x, to be bent downward again at y into the tube Z, which, reaching 

 the depths of the earth, is connected with the channels V. These 

 channels conduct to Z hot water mixed with steam, while R is supplied 

 by the streams S, which lie near the surface, with cold water. The 

 geyser-tube becomes stopped at x by the accumulation from these two 

 sources, and the steam rising from Z, deprived of an outlet, collects at 

 y. Its elasticity being augmented by the masses of steam that keep 

 coming up, and by the continued accession of heat from Z, it forces 

 away the water that is in contact with it, and gradually fills the con- 

 necting passage x y\ and a part of Z, while it interposes a separation 



