OLD FAITHFUL 119 



that superb spectacle has wasted itself on an 

 empty land, and you are solemnly glad that you 

 have seen it. 



And now a word as to the "why." Geysers have 

 been the subject of much scientific investigation, 

 intensely interesting as they are, and the scientific 

 world has generally come to accept the Bunsen 

 theory, that more or less accounts for both the 

 boiling springs and the eruptive springs, or geysers. 

 These springs are long tubes, large or small, 

 filled with water, resting at the bottom, at some 

 unknown depths, on the internal fires of the earth. 

 If the tube be large enough and communication 

 with the surface free, the steam forces its way out 

 gradually, condensing in the water and raising 

 that to the boiling point. These hot springs boil 

 and bubble continually, but, because of the free 

 escape of the steam and its regular condensation, 

 do not, as a rule, overflow their basins. 



And if the geyser tubes are smaellr, circulation 

 is impeded. As the steam forces its way upward^ 

 the condensation ceases. The outlet for the 

 steam is closed; the pressure, already great 



