The Causes and Phenomena of Earthquakes. 57 



an explosion -as to produce a similar effect to that of a bullet 

 passing through a pane of glass. (Familiar Lectures, p. 40.) 

 When a boy, I used frequently to see melted lead cast in plates, 

 and lifted in a molten state from the furnace into a prepared 

 vessel. On such occasions water was sometimes, in play, thrown 

 in small quantities (a drop or two) upon the metal, and the instan- 

 taneous formation of steam was attended, at a certain stage of cool- 

 ing, after the spheroidal state had passed off, by violence and de- 

 tonation. Fouque, however, adds that, if Davy's original theory is 

 true, the heat evolved by Etna in 1865 would have required at least 

 7,000,000 cubic metres of sodium, and therefore an incalculable 

 amount of alkaline metals, to have produced eruptions over the 

 earth from the beginning till now. Lyell very justly remarks, 

 that to sustain the chemical theory would require an amount of 

 knowledge which is altogether unattainable. Louis Soematm 

 (now deceased, and who furnished me with the splendid collection 

 of rocks and minerals in the Museum) remarks that heat would 

 materially modify all chemical combinations, as in the case of 

 mercury, which does not combine with oxygen at ordinary 

 temperatures, but does at boiling point, and then throws it off at 

 incipient red-heat ; " and what is true of mercury is also true of 

 all other elements." 



M. Angeiot between the years 1841 and 1843, read several 

 papers before the Geological Society of France, in explanation 

 of his views respecting the action of sea waters in producing 

 volcanic phenomena. (Bulletin, tomes xiii, xiv, et tome 1. d . s. 



M. F. Martha Beker, also, in 1858 explained to the same 

 Society, how, regarding the definition of Humboldt as the only 

 rational one as to earthquakes being the reaction of the interior 

 of the earth on its exterior envelope, cooling and contraction of 

 cavernous strata of a molecular condition between incandescence 

 and imperfect solidification, producing changes at variable epochs, 

 sufficiently explain all the facts, when connected with the com- 

 bined action of subterranean waters converted into gas. (Tome 

 xv. d.s). 



In a learned Memoir of M. Boue, read in 1856, (Tome xiii, d.s) 

 the author reveiws all the phenomena and the explanations of 

 Hopkins, Perrey, and others, maintaining that earthquakes are in 

 intimate connection with electrical and magnetic forces, (as illus- 

 trated by occurrences of Auroras), an opinion by the way, which 

 finds support in the writings of other and more recent authors, 

 as well as in the notices of earthquakes by Arago and other . con- 

 temporaneous and preceding philosophers. He seeks to combine 

 chemical with magnetic affinities, but admits that some earth- 

 quakes may be due to the pressure of water. 



It would be folly to deny the importance of the facts, or the 

 weight of Boue's reasonings ; but reviewing the great mass of 



