60 Dr, T. Sterry Hunt — Liquefaction of Bocks. 



TV. — The Liquefaction of Eocks. 

 By Dr. T. Sterry Hunt, F.E.S. 



THE number of Scientific Opinion for October 27 (page 457), 

 contains a note by the Eev. Osmond Fisher, calling attention 

 to a suggestion, with regard to the liquefaction of deeply buried 

 rocks, made by him in a paper read before the Cambridge 

 Philosophical Society in April, 1868, and since published in the 

 Transactions of that Society, In a notice of this paper by him, in 

 the Geological Magazine for November, 1868, Mr. Fisher insists 

 that deeply buried and intensely heated portions of rock, which, in 

 accordance with the conclusions of Mr. Hopkins, are kept in a solid 

 state by great pressure, may, by a diminution of pressure consequent 

 upon movements of the earth's crust, assume a liquid condition, and 

 thus give rise to lavas. This suggestion is however claimed by Mr. 

 Scrope, in a communication to the same Magazine for December, 

 1868, as his own, and as having been put forward by him in both 

 editions of his now classic work on Volcanos. This statement of 

 Mr. Scrope was questioned by Mr. Fisher in the Geological 

 Magazine for January, 1869, and Mr. Scrope does not appear to 

 have replied. In a paper in the same magazine for June, 1869, I 

 have referred to this view as belonging to Mr. Scrope, and as also 

 advocated by Mr. Fisher, who has availed himself of the republica- 

 tion of my paper in Scientific Opinion for October 20, to re-assert his 

 claim to be the originator of this view, and to demand either of Mr. 

 Scrope or myself some justification of our assertions. 



I might leave to Mr. Scrope the task of vindicating himself, and 

 rest, so far as I am concerned, upon his statement in the Geological 

 Magazine for January, 1868, but having before me Mr, Scrope's 

 book on Volcanos (edition of 1862), I venture to call attention to a 

 passage therein, which has probably escaped Mr. Fisher's notice, 

 where Mr. Scrope concisely speaks of " the extravasation and 

 ebullition of subterranean mineral matters (known, so far as we are 

 acquainted with them, to contain water), which increased tempera- 

 ture or diminished pressure has liquefied and caused to effervesce " 

 (page 309). Elsewhere he speaks of the imperfectly liquid con- 

 dition of the matter underlying a volcanic vent, as varying from 

 time to time " according to circumstances of temperature and 

 pressure," and proceeds to show that " changes in position, hulk, 

 weight, cohesion, and consequent resistance of the rocks above " are to 

 be considered, as well as the variations in the rate of heat from 

 below (page 266). These passages, in which I have italicised 

 certain words, will, I think, establish Mr. Scrope's claim of priority 

 over Mr. Fisher, whose excellent memoir has merits enough, which 

 are wholly his own. 



According to Mr. Scrope's view, rocks may be melted either by 

 increase of heat or by diminution of pressure, and congealed by 

 diminution of heat or by increase of pressure. This would, doubt- 

 less, be the case if the simple igneous fusion of anhydrous rocks 



