302 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



period, then reheating in the laboratory could discover no "explo- 

 sive " rocks. The distinction " dead " rocks and " live " or " explo- 

 sive " rocks loses all significance so long as it applies merely to rocks 

 containing gases in virtual equilibrium with each other, which merely 

 release the gas when heated. But immediately we understand that 

 in lavas carrying gases in solution or mechanical imprisonment the 

 gases shut up therein may react together, with release of heat, the 

 moment they are free to do so, " explosive "' lava has a definite mean- 

 ing, and Brun's experience (loc. cit., p. 55), that " once the expansion 

 has commenced nothing [for example, withdrawal of the source of 

 heat] can stop it," becomes a most illuminating one. Rapid expan- 

 sion of the reacting gases, together with the weakening of the inclos- 

 ing walls through the accession of heat thus supplied from within maj- 

 very well produce explosive phenomena, in the sense in which Brun 

 used the term, either in nature or in the laboratory. It is otherwise 

 somewhat difficult to see how simple adiabatic expansion of a gas in- 

 closed in walls of obsidian, which are very viscous even at very high 

 temperatures, can produce " explosions " in the manner postulated 

 by Brun. 



WATER AND THE BASIC MINERALS. 



There is another conclusion which has been freely otfered by those 

 who hold to the view that HoO can not be present as such in the 

 emanations from active volcanoes, of which a statement may be 

 found in the quotation from Green in the opening paragraph of this 

 paper. It states that " the basic minerals themselves give no indica- 

 tions, in the main eruptions, of having been in contact with water, 

 highly siisceptihle as they are to such an influence. '' 



It apiDears reasonably certain that the italicized portion of this 

 quotation (italics are ours) is dictated by the relation between basic 

 rock, liquid water, and air at comparatively low temperatures, and 

 to this extent it may very well be true. In the active volcano Kilauea, 

 however, we are dealing with gaseous HoO at a temperature above 

 1,000° ; this is quite another matter. It is a part of our program to 

 endeavor to supply the lack of proper data about the relation between 

 the several gases found and the chief ingredients of the li(iuid lava, 

 and in view of the absence of such data at the present moment the 

 question raised can receive no very complete answer. It is, neverthe- 

 less, a comparatively simple matter to bring the powdered lava and 

 water together at 1,100° in the absence of oxygen. The result ap- 

 pears to support our view, for after several hours of the most in- 

 timate contact between the gaseous H2O and the lava no chemical 

 change whatever could be detected either in the "basic minerals" 

 or the water. In so far as a qualitrftive experiment of this kind may 



