GEYSERS 



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occupied the place of the cave having been carried away 

 in solution by the water. There are thousands of caves 

 of this kind but perhaps the most noted in this country 

 are Mammoth Cave with its nearly 200 miles of under- 

 ground avenues and grotesquely sculptured halls, and 

 Luray Cave with its wonderful stalactite and stalagmite 

 decorations. Sometimes the top of one of these caves is 

 nearly eroded away, leaving a part of its old roof standing 

 as a natural bridge, such as the natural bridge of Virginia 

 or of Utah. Sometimes the top falls in, leaving a sink-hole. 



152. Geysers. Experiment 128. 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 (b) > 

 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. 



Through the tube (b) 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 (b) . Now 

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

 out of the tube (b) 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. Thus a 

 spray of hot water is intermittently ejected from the flask as long as 

 heating continues. We have here an action which resembles that of 

 a geyser. 



112. 



