108 The Ohio Journal of Science [Vol. XIX, No. 2, 



The linear arrangement in such cases may not be significant, 

 therefore, but v/hen there is no superficial break in the tuff cor- 

 responding to the line of smokes, it is difficult to explain their 

 arrangement in any other way than as being outlets of a funda- 

 mental fissure in the bed rock. The writer, at least, can imagine 

 no possible means by which such lines of smokes, often more 

 than a mile in length, could be explained on the surface water 

 hypothesis. 



But although the volume of the emanations, their chemical 

 character, their temperatures and their arrangement all give 

 very clear and positive indications that they are true volcanoes, 



Photograph by R. F. Griggs 



LINES OF FUMAROLES ACROSS THE VALLEY. 



A portion of the valley floor where the linear arrangement of the fumaroles is 



very conspicuous, indicating that they spring from fissures traversing 



its floor or encircling its edges. 



we were very unwilling to consider the matter settled until 

 we could find ocular evidence of their actual emergence from 

 orifices in the bed rock underlying the Valley. 



But this proved to be a matter of considerable difficulty, 

 for the Valley is everywhere filled with a very thick deposit 

 of the peculiar tuff which is discussed in the succeeding paper. 

 There was good reason to believe, as will be seen, that the smokes 

 did not originate in the tuff itself, but it so plasters up the 

 Valley that it is difficult to ascertain the character of the ground 

 from which they do emerge. As we prosecuted the exploration, 

 therefore, we were constantly on the watch for evidence which 

 would throw light on the source of the vapors. 



