422 EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



below the surface, contains sufficient heat to account for the geyseric 

 phenomena, or else that the geyser tube has some opening either at the 

 bottom or on the sides, by which steam and superheated water have 

 access to it from a considerably greater depth where the temperature is 

 very high. At these depths caverns probably exist. In "Frost and 

 Fire," i>age 417, Vol. II, it is stated that in the tube of the Great Geyser 

 of Iceland, at a depth of 45 feet from the surface, there is a ledge which 

 was first discovered by Mr. Bryson, of Edinburgh. From beneath this 

 ledge steam bubbles rise while the geyser tube is filling, and a ther- 

 mometer sunk a few feet below it was lifted and driven about like " a fish 

 in a flurry," and when brought to the surface was found to be broken. 

 The conclusion is that steam or hot water or both enter the tube from 

 the side just beneath this ledge, for when the thermometer was sunk 

 lower it remained quiet. Here, then, we have an explanation of the 

 quiet and safe condition of Bunsen's thermometer at the bottom of the 

 geyser during a great eruption (see i)age 421). Strockr has openings 

 on opposite sides of its tube, and when empty, water and steam can 

 be seen pouring into it from both apertures. In Fig. 32, taken from 

 " Frost and Fire," sections of both Strockr and Geyser are shown. The 

 point 45 feet below the surface is important in Bunsen's theory, and 

 here is the ledge from beneath which water and steam are supposed to 

 enter the tube. The Great Geyser is usually full of water, and conse- 

 quently its internal constructiou cannot readily be examined, but there 

 is little doubt that it is similar to that of Strockr, i. e., it consists of a 

 tube with a conduit or conduits leading to subterranean cavities. That 

 such cavities exist is more than probable. On page 405 1 have indicated 

 my belief, that all geysers are opiginally due to a violent outburst of 

 steam and water, and, under such conditions, irregular cavities and 

 passages are more likely to be formed than regular tubes. As a fact, 

 geyseric action on a small scale, dependent on an arrangement of cavi- 

 ties and tubes, may be simulated by heating water and plaster of Paris 

 together in a tin pan. For details of such experiments, see pages 405- 

 407 of " Frost and Fire." 



In view of what we have just written, Bunsen's conclusion (No. 2) given 

 on page 418, would have to be modified somewhat. His conclusion was 

 that, at no point in the tube did the water attain the temperature of 

 ebullition which it should have under the pressure to which it is sub- 

 jected. As far as this relates to the straight tube in which his tempera- 

 tures were taken, it may be so ; but if he could have taken temperatures 

 in the side conduit, I have little doubt he would soon have reached a point 

 where the temperature would not only be at the boiling point for tbat 

 depth but even exceed it. In the Yellowstone Park we obtained a 

 number of surface temperatures which were above the boiling point. 

 In the Great Geyser of Iceland, the mass of water in the tube prevents 

 this condition at the surface, and when it takes place opposite the aper- 

 ture an eruption is caused. In the main, however, I am inclined to 

 accept Bunsen's theory, especially as it seems to me to require subter- 

 ranean cavities in which the water must be heated. Whether these are 

 caverns, enlargements of tubes, or sinus channels, appears to me to be 

 of no consequence, except as the interval or period of the geyser might 

 be affected by the form of the reservoir holding the water. In the fol- 

 lowing chapter a few points relating to variations of the water supply 

 are given. 



