TRANSACTIONS OF THE SECTIONS. 105 



rally studied, that theory would not appear startling. lie had considered the objec- 

 tions of Bischof and others to chemical theories, and he believed that they did not hit 

 the explanation he proposed. That explanation attributes the force of volcanic action 

 to solar energy, stored up in rocks by buried organic matter — this organic matter 

 either existing in rocks as carbon and carbonaceous compounds, or represented by 

 sulphides and other substances, produced by the reducing-action of organic matter. 

 Volcanoes, as has been said of steam-engines, are worked by " the light of other days." 

 Starting from the five groups of well-preserved extinct volcanoes in Spain and Por- 

 tugal, proceeding to consider the volcanoes of the Mediterranean basin, and finally 

 volcanoes in general, the author concluded that, as had been pointed out by Steny 

 Hunt, volcanoes, as a rule, lie on or at the border* of much sedimentaiy rock ; and 

 the exceptions to this rule he considered to be explicable in conformity with his 

 theory. These sedimentary rocks, especially in the Mediterranean basin and under 

 the volcanoes of Catalonia, could be said to contain much organic matter. Next 

 he examined the alleged fact of the occurrence of volcanoes along great lines of 

 fissure, and concluded that their occurrence in lines was due to their connexion with 

 the sea, as well as with lines of sedimentary deposition. The author believes that 

 the sometimes alleged identity of volcanic rocks was a statement either misleadino- or 

 meaningless, and that the composition of volcanic rocks was just what we sho^uld 

 expect, if they were formed from masses of sedimentary rocks, in presence of sea- 

 water. Proceeding to the consideration of the results of Fouque, Deville, Daubeny, 

 and others, regarding the gaseous products of volcanoes, he showed that these afforded 

 striking evidence that a mixture of gases, similar to that evolved in gasworks, was 

 oxidated in volcanoes with production of great heat. To this heat, and to the 

 burning of separated_ carbon, sulphur, and probably iron, he attributed the hio-h 

 temperature present in some lava on its appearance in tlie air. From the researches 

 of Sorby, Zirkel, Daubree, Delesse, Stoppani, and others on the subject of lavas, he 

 concluded that these were formed at moderate temperatures, and only exceptionally 

 fused by the great heat produced in the crater. The enormous amount of heat 

 assumed to be present in volcanic action was, in the author's opinion, in great part 

 mythical, and what was actually ascertained could be explained by the nature ofthe 

 substances oxidating in the earth and burning at the crater. As to the introduction of 

 air and water, he referred to the penetration of sea- water at Cephalonia, to the re- 

 searches of Delesse, to the Catalan trompe, and to the fact that sea- water dissolves 

 much o-xygen; while the nitrogen evolved, in volcanic areas and elsewhere, is 

 usually either pure or accompanied by less oxj-gen than would compose atmo- 

 spheric air. He then pointed out that the amount of carbon found in rocks might 

 be adequate to produce all the heat required, if we assumed the rocks to have been 

 rapidly deposited ;_ whereas, if they had been slowly deposited, the amount of car- 

 bon now existing in them could only be a remaining fraction of that they formerly 

 contained, the rest having been evolved as carbonic acid. If he were to reject geolo- 

 gical time, as some have done, he might assume that the volcanic heat to be accounted 

 for was j list as much as the average amount of carbon was adequate to supplj-. After 

 attributing the origin ofthe vast amount of buried carbon now in rocks to buiied car- 

 bon in former rocks, and remarking that it must have passed very gradually throuo-h 

 the atmosphere, he discussed some correlated processes in nature which would keep 

 volcanic action roughly uniform, the sun-force continually passing through oroanic 

 matter into volcanic heat. He confined himself chiefly to volcanic action'^proper as 

 that was generally considered the best evidence of the original-heat theory ; but he 

 considered that such general internal heat as had been ascertained might be attri- 

 buted to the distribution of volcanic heat by water, to general oxidation of the car- 

 bon ahnost universal in rocks, to friction as shown by Bianconi, and finally, to the 

 electric currents ascertained to exist in the earth, and to be probably produced in 

 great part by the sun. 



The paper was illustrated by sketches taken by the writer in the Two Sicilies, 

 the Greek Isles, Catalonia, &c., also by some curious specimens of metamorohosed 

 gla.5s, which he had found while excavating for antiquities in Ischia. 



