426 REPORT UNITED STATES GEOLOGICAL SURVEY. 



this subject of sympathy remind us of Horrebow's statement as to the 

 Great Geyser of Iceland. He says that if water from the geyser be put 

 into a bottle, whenever the geyser has an eruption the water in the bottle 

 will also be agitated, and if it be corked will burst. 



GENERAL CONDITIONS NECESSARY FOR GEYSERS. 



Before closing this chapter we will briefly recapitulate the general 

 conditions that appear to be necessary to the existence of geysers. The 

 special conditions are detailed in the preceding chapters. 



1. The presence of igneous rocks which still retain their heat at a 

 considerable distance below the surface. We have seen that if the heat 

 at the surface is too great, stufas are the result, and that geysers are 

 found where volcanic action is extinct or becoming dormant. 



2. The presence of meteoric water which shall have access to the hot 

 rocks which convert it into steam in part at least. 



3. A tube, by means of which this heated water, with other meteoric 

 water, can reach the surface and appear as a geyser. 



Bunsen's idea was that the formation of a siliceous geyser tube was 

 necessary, and that prior to the formation of this siliceous tube the 

 spring was a simple thermal spring. The experiment demonstrating his 

 theory proves the fallacy of this idea. In the Gibbon Geyser Basin also 

 we have additional iDroof against this idea in the Steamboat Yent or 

 Geyser, which has so recently begun the formation of geyserite that in 

 1878 it showed only as small points of deposit on surrounding rocks. 

 Any tube will supply the necessary conduit to the surface, and we need 

 not suppose that it is perfectly regular either in shape or size. The re- 

 verse is undoubtedly the condition in the majority of the geysers of the 

 Yellowstone National Park. 



