Juue] HUNT — ON VOLCANIC ACTION. 1G9 



exciting cause of the chemical changes which take place in the 

 buried sediments. The notion of a subterranean combustion or 

 fermentation, as a source of heat, is to be rejected as irrational. 



A view identical with that of Keferstein, as to the seat of 

 volcanic phenomena, was soon after put forth by Sir John 

 Herschel, in a letter to Sir Charles Lyell, in 1836 (Proc. Geol. 

 Soc. London, ii. 548.) Starting from the suggestion of Scrope 

 and Babbage, that the isothermal horizons in the earth's crust 

 must rise as a consequence of the accumulation of sediments, he 

 insisted that deeply buried strata will thus become crystallized 

 by heat, and may eventually, with their included water, be raised 

 to the melting point, by which process gases would be generated, 

 and earthquakes and volcanic eruptions follow. At the same 

 time the mechanical disturbance of the equilibrium of pressure, 

 consequent upon a transfer of sediments, while the yielding sur- 

 face reposes on matters partly liquified, will explain the 

 movements of elevation and subsidence of the earth's crust. 

 Herschel was probably ignorant of the extent to which his views 

 had been anticipated by Keferstein ; and the suggestions of the 

 one and the other seemed to have passed unnoticed by geologists 

 until, in March, 1858, I reproduced them in a paper read before 

 ■ the Canadian Institute (Toronto,) being at that time acquainted 

 with Herschel's letter, but not having met with the writings of 

 Keferstein. I there considered the reaction which would take 

 place under the influence of a high temperature in sediments 

 permeated with water, and containing, besides silicious and 

 aluminous matter, carbonates, sulphates, chlorids, and car- 

 bonaceous substances. From these, it was shown, might 

 be produced all the gaseous emanations of volcanic districts, 

 while from aqueo-igneous fusion of the various admixtures 

 might result the great variety of eruptive rocks. To 

 quote the words of my paper just referred to : " We 

 conceive that the earth's solid crust of anhydrous and primitive 

 igneous rock is everywhere deeply concealed beneath its own 

 ruins, which form a great mass of sedimentary strata, permeated 

 by water. As heat from beneath invades these sediments, it 

 produces in them that change which constitutes normal meta- 

 morphism. These rocks, at a sufficient depth, are necessarily 

 in a state of igneo-aqueous fusion ; and in the event of fracture 

 in the overlying strata, may rise among them, taking the form of 

 to eruptive rocks. When the nature of the sediments is such as 

 Vol. IV. M So. 2. 



