THE 



JOURNAL OF GEOLOGY 



MAY-JUNE, igo6 



VOLCANOS AND RADIOACTIVITY^ 



MAJOR C. E. BUTTON, U. S. A. 



One of the commonest, and perhaps the most impressive, of natu- 

 ral phenomena, the volcano, has hitherto been without any explana- 

 tion of its cause, though it has been before the world a subject of theory 

 for many centuries. The reason for this is quite apparent. We 

 perceive the action of the volcano upon the surface, and we know what 

 it does. But the theater of its origin and the development of its energy 

 are far below the surface of the ground, out of reach of inspection or 

 direct observation. Human ingenuity has been baffled in its efforts to 

 explain the phenomenon because of the want of observed facts and the 

 impossibility of obtaining them. Bjit, while we are, and probably 

 always shall be, unable to directly inspect the seat of origin of the 

 volcanos, there are 'certain inferences in connection with them which 

 have attained a degree of probability which entitles us to use them as 

 facts which may limit speculation and confine it within very narrow 

 boundaries. I purpose to mention these inferences in order to see the 

 general nature of the solution to which they point ; for, unless I am 

 greatly mistaken, they will show us that we are close upon the verge 

 of a solution. 



I. The first fact to be mentioned is the solidity of the earth. It 

 is so well known that I shall not dwell upon it, and merely mention it 

 in order to bring it, together with other facts, into the same series 

 or group. 



I Read before the National Academy of Sciences, April 17, igo6. 

 Vol. XIV, No. 4 259 



