62 THE PROBABLE SEAT OF VOLCANIC ACTION. [VI. 



to the infancy of geology. To this period belong the theories 

 of Lemery and Breislak. (Cosmos, V. 443 Otte's translation.) 

 Keferstein, in his Xaturgeschichte des Erdkorpers, published in 

 1834, maintained that all crystalline non-stratified rocks, from 

 granite to lava, are products of the transformation of sediment- 

 ary strata, in part very recent, and that there is no well-defined 

 line to be drawn between neptunian and volcanic rocks, since 

 they pass into each other. Volcanic phenomena, according to 

 him, have their origin not in an igneous fluid centre, nor in an 

 oxidizing metallic nucleus (Davy, Daubeny), but in known 

 sedimentary formations, where they are the result of a peculiar 

 kind of fermentation, which crystallizes and arranges in new 

 forms the elements of the sedimentary strata, with an evolu- 

 tion of heat as a result of the chemical process. (Naturgeschichte, 

 Vol. I. p. 109 ; also Bull. Soc. Geol. de France (1), Vol. VII. 

 p. 197.) In commenting upon these views (Am. Jour. Science, 

 July, 1860), I have remarked that, by ignoring the incandes- 

 cent nucleus as a source of heat, Keferstein has excluded the 

 true exciting cause of the chemical changes which take place in 

 the buried sediments. The notion of a subterranean combus- 

 tion 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 suggestions 

 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 in- 

 cluded water, be raised to the melting point, by which pr 

 gases would be generated, and earthquakes and volcanic erup- 

 tions follow. At the same time the mechanical disturbance of 

 the equilibrium of pressure, consequent upon a transfer ot 

 ments while the yielding surface reposes on matters partly 

 liquefied, will explain the movements of elevation and sul>si<l -m < 

 of the earth's crust. Herschel was probably ignorant of the 



