2$0 



SCIENTIFIC NEWS. 



[Sept. 14, I J 



then it seemed to him that in those thicknesses of rock which they 

 were able to examine and test by the most minute methods of obser- 

 vation—he meant the stratified rocks — they would find evidences of 

 certain strata in which there were no traces whatever of strain. As 

 a geologist, he was bound to believe there were no such strata. His 

 experience of the ancient history of the earth practically amounted 

 to this, that the very deepest, the very oldest of the stratified rocks 

 were those which had suffered the greatest amount of crumbling, the 

 greatest amount of physical change, the greatest amount of folding. 

 In other words, those which were sunk deepest were those which 

 were compressed most. He found no trace whatever of this layer 

 under consideration. Now for another point. It seemed to him that 

 the condition of the interior of the earth was not to be made out by 

 any mathematical assumptions, but it seemed to him they wfre 

 really in the position of forming some definite idea from the modern 

 development of stellar chemistry, of the application of spectrum- 

 analysis to make out the physical constitution of the sun and stars, 

 the planets, the meteorites, and the moon. And when from this he 

 knew that space was full of bodies in various conditions of heat ; 

 when he knew that the planets varied from one another in their de- 

 grees of heat ; when he knew that the moon was absolutely cold and 

 lifeless, but that its physical constitution showed that in ancient 

 times it was intensely hot ; when he turned to meteorites, and saw 

 before him heavy metallic and stony masses, which, at the time they 

 were revolving in space and before they became entangled in the 

 earth's atmosphere, were cold, ar.d yet, which they knew from their 

 very physical constitution, were originally intensely hot; when 

 he knew all this he was bound to believe that there was a general law 

 by which there was a steady loss of heat, and by which the intensely 

 heated bodies gradually grew colder and colder, until at last even 

 such a mass as the sun himself would become as cold as the meteor- 

 ites. In the face of all such evidence it was wholly impossible for 

 them to believe that the cooling of the earth was to be stopped at 

 the 400 miles limit. The President devoted some further remarks 

 to this subject, couched in the same tenour, and concluded by 

 pointing out how appropriate it was they should be discussing the 

 question of volcanic phenomena in that room, for it was at the last 

 Bath meeting, in 1864, that the President of that section was his old 

 master — Professor Phillips — and Professor Phillips was the historian 

 of Vesuv ius. 



Dr. Johnston-Lavis said that volcanologis's could trouble 

 themselves but little about the interior of the earth, their time being 

 taken up with studying the phenomena themselves, the origin of the 

 material thrown up, and its cooling at the sur'ace. He nevertheless 

 rejected all Professor Claypole's theories, both because they assumed 

 the crust of the earth to be one uniform mass and of one uniform 

 thickness. He protested, also, against the theory that earthquakes 

 and volcanic ac ivity were confined to a depth of five miles, which, 

 on the showing of the "no strain" zone, they would be. His ex- 

 perience led him to believe that the distribution of earthquakes on 

 the surface was in proportion to their depth. The great Charles- 

 ton earthquake, he believed, to have a depth cf at least twelve 

 miles, whde other earthquakes of limited area he believed to be 

 similarly limited in depth. To suppose that vast earthquakes, 

 spreading overhundieds and thousands of miles, were limited to five 

 miles depth was impossible ; and he did not know how mathemati- 

 cians could make such an assertion. With regard to the origin of 

 volcanic action, he attributed the large amount of literature on the 

 subject to impfrfect information, and he entered a strong protest 

 against the peifunc'ory system that some have of pretending to in- 

 vestigate these phenomena, saying that, before a proper opinion 

 could be formed, it was necessary to be on the watch night and day 

 for years together. Volcanic activity, he believed, did bear a rela- 

 tion to the barometer and the thermometer. It had been statisti- 

 cally proved that there was a definite relation between volcanoes 

 and the tide and the position of the moon. For five years he had 

 carried out a daily record at Vesuvius, and he found distinct evi- 

 dence that the activity of the volcano was in most remarkable rela- 

 tionship to barometric pressure. As for the' theory of the gradual 

 percolation of water to the heated mass, he regarded it, to say the 

 least, as a very crude theory. 



Professor Claypole agreed with most of the objections which 

 had been taken. No evolutionist could for a moment doubt the 

 truth of the law of cooling which the President had referred to ; but 

 nevertheless, the President's objection was like a pyramid standing 

 on its apex— it had no foundation. The mathematicians never in- 

 tended it to be understood that cooling entirely ceased at 400 miles 

 limit— they would be the last to accept such a corollary. What the 

 mathematicians meant was this — that in discussing one of these in- 

 tensely difficult mathematical problems their formularies became so 

 long and complicated that they were bound to leave out all elements 

 not absolutely necessary ; and by drawing the line at 400 miles they 

 meant— not that cooling would entirely cease there, but — that beyond 



that line the radiation into space was so small as to be utterly un- 

 appreciable and valueless in regard to their calculations. In regard 

 to the convection currents, he would reply that he must be a hardy 

 geologist in the present day who would maintain that the earth is 

 liquid enough for the convection currents to occur at a depth of 403 

 miles. 



A paper was read On the Causes of Volcanic Action, for Mr. J. 

 Logan Lobley, F.G.S. After citing recent opinion as to the 

 absence of an adequate explanation of the causes of volcaric action, 

 the author showed that the accumulation of knowledge of the con- 

 trolling facts of volcanic phenomena and the amount of attention 

 which had been given to the question placed the subject on firmer 

 grounds, and made the finding of a sa'isfactory solution of the prob- 

 lem now more probable. 



The difficulty of the question lay in the great number of facts and 

 the apparent conflict of many of them. 



It was, in the first place, necessary that the leading and control- 

 ling facts should be recognised and kept in view. With this object 

 a compendium or concise statement of forty-two such facts was given, 

 followed by a brief review of the various theories that had been 

 advanced, from Lemery's in 1700, to Prestwich's in 1886, with in 

 each case numerical references to the facts in the compendium which 

 were, in the author's opinion, at variance with the respective hypo- 

 theses. 



The author's own conclusions were then submitted, which are, 

 briefly, as follows : — 



A. That the primary cause of the formation of lava is the internal 

 heat of the globe inducing chemical action in subterranean regions 

 where the materials and conditions are both favourable. 



That since the fusion-point of temperature of solids is raised by 

 extreme pressure, conditions for chemical action may be changed 

 from unfavourable to favourable by the removal or relief of vertical 

 pressure by lateral or tangential pressure. 



That certain substances are fusible at low or moderate tempera- 

 tures, and that thus at very moderate depths chemical action may 

 be locally commenced that will ex'end until sufficient heat is pro- 

 duced to effect rock-fusion. 



B. That the cause of the ejection of lava from its source, and its 

 rise in the volcanic tube is the increase of bulk consequent upon the 

 change from the solid to the fluid state, aided by the formation of 

 potentially gaseous compounds by chemical reactions among the 

 original materials of the magma. 



That the ascent of the lava in the volcanic tube may be effected 

 by the weight of the atmosphere and by lunar attractive influence, 

 and that therefore a volcanic vent is a thermometer, and, second- 

 arily, a barometer and helkusometer* combined. 



C. That the explosive effects of volcanic eruptions are altogether 

 secondary, and are due to the access of sea and land water to 

 fissures, by percolation through cool rocks, up which lava is 

 ascending. 



That this water, when converted into steam, opens, by its ex- 

 pansive power, rents that admit large flows of sea-water to the lava, 

 occasioning the formation of vents and the greater explosive phe- 

 nomena of eruptions. 



The formation of the actual surface volcano and the determina- 

 tion of its position is therefore due to the sea, near which volcanoes 

 are almost always situated. 



Emissions of lava without explosive effects are from volcanic tubes 

 to which large flows of water have not obtained admittance, and, on 

 the other hand, purely explosive eruptions, without lava flows, are 

 caused by water reaching lava which fails to rise to the surface of 

 the earth. 



The various forms of volcanoes the author considered could be 

 explained by these views, which opposed — 



1. An infra-crust common central source of lava. 



2. The passage of lava through thirty miles of recks, and conse- 

 quently through any greater thickness. 



3. The ejection of lava from its source by vertical pressure. 



4. The ejection of lava from its source by super-heated steam or 

 ''potential steam " force. 



5. The passage of water through highly-heated rocks, either by 

 fissures or by capillary transmission. 



6. The accumulation or the presence of water at volcanic foci. 



7. A primogeneal "water substance." 



8. The importance of land surface water. 



The author has given much thought during many years to volcano- 

 logy, and had made personal observations of volcanic activity ; and 

 whether his views were approved or not he would be glad if they 

 elicited facts and opinions that would further a solution of the problem. 

 He thought a discussion on the subject would not be inappropriate 

 at the city of Bath, famous as it was for thermal waters deriving 



* From JAkOo-is — ews= attraction. 



