512 



WITHIN THE EARTH'S CRUST 



outrushing of the water for a time varying from a few minutes 

 to between one and two hours. Then it gradually quiets 

 down and dies away into a bubbling spring of hot water. 



The time at which most geysers will erupt is uncertain, 

 but there is one, Old Faithful, in Yellowstone Park, which 

 is almost as regular as a clock, the time between its erup- 

 tions being a little over an hour. This geyser plays to the 

 height of about 150 feet and maintains the column of water 

 for about four minutes. The Giant Geyser of the same re- 

 gion throws a large column of water to a height of 250 feet. 

 It plays from one to two hours. 



Experiment 161. Fit a 250 cc. glass flask with a two-hole rubber 

 stopper. Through one hole extend a glass tube (a) almost to the 



bottom of the flask and through the 

 other hole a tube (6), 5 or 6 cm. longer 

 than the height of the flask, to within 

 about 1 or 2 cm. of the bottom of 

 the flask. This last tube should be 

 slightly drawn out at the end and 

 bent at the top so that it slants away 

 from the flask. Arrange the flask on 

 a ring stand so that it can be heated 

 by a Bunsen burner. Connect to the 

 tube (a) a rubber tube long enough 



to reach into a water reservoir placed higher than the top of the 

 flask and to one side. Fill the reservoir with water. (Figure 170.) 

 Through the tube (6) " suck " the air out of the flask until the 

 water from the reservoir begins to run into the flask. A siphon will 

 be formed which, when there is no internal pressure, will keep the 

 water in the flask slightly above the bottom of the tube (6) . Now 

 heat the flask. When steam begins to form, hot water will be 

 thrown out of the tube (6) until its lower end becomes uncovered 

 and the pressure of the steam relieved. Water from the reservoir 

 will then run in again, slightly covering the end of the tube. As 

 soon as more steam is formed, hot water will be ejected as before. 



FIGURE 170 



