402 



SCIENCE. 



[N. S. Vol. XXIV. No. 613. 



higher temperatures. If the supply of water 

 holds out above, the fused region will enlarge 

 downward and laterally until, with excessive 

 size, the rigidity of its confines breaks down. 



To keep water liquid at 200° C. it is merely 

 necessary to tap the ocean at a level greater 

 than 500 feet below the surface, while a depth 

 of five miles of water may be available. The 

 200° isotherm may also be put at a distance 

 of about five miles below the solid surface, 

 but it is correspondingly lifted up on the 

 shores of the ocean. Near the ocean, there- 

 fore, this earth level is potentially fused, if 

 by whatever catastrophe the ocean penetrates 

 as far as the 200° isotherm, barring the 3,000 

 atmospheres of pressure which one may as- 

 cribe to the given depth of the isotherm below 

 the surface. In view of the rigidity of rock, 

 such pressures are not yet irresistible, when 

 burdening the solid framework of a region 

 not too large. The effective pressures are 

 smaller. Fusion will depend upon the char- 

 acter of the rock magma found in place; it 

 will be rapid if basic, slow if acid, but will 

 in every case constitute a local source of heat, 

 since as in Thomson's case, the region of reac- 

 tion is nicely jacketed in a way to guarantee 

 the utmost amount of mischief. More than 

 this; water-glass becomes saturated subject to 

 temperature and pressure, after which the 

 heat reaction ceases, and the chances for vul- 

 canism become extinct. Furthermore, there 

 is a chance for periods. Finally one would 

 expect the region of volcanic activity to 

 correspond in depth with the depth of the 

 ocean; and again to be on the margin of the 

 ocean without being necessarily absent in the 

 interior of continents. Could anything be 

 more cleverly dovetailed? What if the 

 heathen rage and say ' qualitative ' or ' inade- 

 quate ' ; what if throughout all the turmoil of 

 the Pelee eruptions, not a soul has thought it 

 worth while to quote my results. I am now 

 doing this myself. 



But Elihu Thomson will have none of it. 

 * No water would enter a hot stratum unless 

 forced in by pressure in excess of that which 

 the steam would acquire upon its generation,' 

 etc. Unfortunately we have to do with much 



more than a mechanical phenomenon. The 

 chief pressures in question are capillary and 

 osmotic pressures. Steam will pass through 

 porous rock against very considerable pres- 

 sures.* I remember that I once had an occa- 

 sion to pass a very fine spray of air through 

 water. Nothing seemed simpler: I tried to 

 force the air through a submerged cup of 

 unglazed porcelain. But it would not work! 

 A little consideration showed me afterwards 

 that it takes ten atmospheres to do that, and 

 the wretched old trap blew up before this 

 pressure was reached. Through dry porce- 

 lain the air escapes jauntily enough, but it 

 will not do so if the pores are stoppered with 

 water. One may estimate in the same way 

 that pores of molecular dimensions, as in 

 case of osmotic phenomena, and diffusion 

 would call for many thousands of atmos- 

 pheres if water is to be forced through, -so 

 that the pump which feeds the vulcanic boiler 

 to use Thomson's image, is not a cast-iron 

 contrivance. But apart from this, having once 

 fused my glass I am at liberty to putty up 

 every fissure that may interfere with my busi- 

 ness. I am quite unwilling to leave Elihu 

 Thomson a single crack to puff away my 

 steam, unless it be the cataclysmal break-up 

 by which my glass, pumiced or not, or any of 

 its ingredients, water and mud, are finally 

 ejected. Here I can accommodate him period- 

 ically. 



Major C. E. Button's recent article^ breaks 

 off entirely with his old-fashioned comrades, 

 and looks at volcanoes from a new point of 

 view. I always read Button at arm's length: 

 when I differ from him, lest the trenchancy 

 of his style rob me of the charm of my own 

 convictions. And the case here in question- 

 is even more disquieting. Whoever invokes 

 radio-activity silences most of us; for if the- 

 incantation be potent enough, there is very 

 little that the wily electron can not do. But 

 in this instance, not a few have been in quest 



* I have not the data at hand, but they wilP 

 be found, if I remember, in Oscar Peschel's * Erd-^ 

 kunde.' 



' ' Volcanoes and Eadioactivity,' Nat. Academy^ 

 April 17, 1906. 



