16 OX SOME POINTS IN CHEMICAL GEOLOGY. [II. 



tained by argillaceous sediments), and is in part formed by the 

 action of heat upon azotized organic matter present in these 

 strata, as already maintained by Bischof.* Nor can we hesi- 

 tate to accept this author's theory of the formation of boracic 

 acid from the decomposition of borates by heat and aqueous 

 vapor, t 



The metamorphism of sediments in situ, their displacement 

 in a pasty condition from igneo-aqueous fusion as plutonic 

 rocks, and their ejection as lavas, with attendant gases and 

 vapors are, then, all, results of the same cause, and depend 

 upon the differences in the chemical composition of the sedi- 

 ments, the temperature, and the depth to which they are buried : 

 while the unstratified nucleus of the earth, which is doubtless 

 anhydrous, and, according to the calculations of Messrs. Hop- 

 kins and Hennessey, probably solid to a great depth, intervenes 

 in the phenomena under consideration only as a source of 



* Lehrbuch der Geologic, Vol. II. pp. 115-122. 



+ Ibid., Vol. I. p. 669. 



The notion that volcanic phenomena have their seat in the sedimentary 

 formations of the earth's crust, and are dependent upon the combustion of 

 organic matters, is, as Humboldt remarks, one which belongs to the infancy 

 of geognosy. (Cosmos, Vol. V. p. 443. Otte's translation.) In 1834, Christian 

 Keferstein published his Naturgeschichte des Erdkorpers, in which he main- 

 tains that all crystalline non-stratified rocks, from granite to lava, are products 

 of the transformation of sedimentary 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 an oxidizing metallic nucleus, 

 but in known sedimentary formations, where they are the result of a peculiar 

 process of fermentation, which crystallizes and arranges in new forms the ele- 

 mente of the sedimentary strata, with evolution of heat as an accompaniment 

 of the chemical process. (Naturgeschichte, Vol. I. p. 109 ; also Bull. Soc. 

 Geol. de France (1), Vol. VII. p. 197.) 



These remarkable conclusions were unknown to me at the time of writing 

 this paper, and seem indeed to have been entirely overlooked by geological 

 rs ; they are, as will be seen, in many respects an anticipation of the 

 views of Herschel and my own ; although in rejecting the influence of an 

 incandescent nucleus as a source of heat, he has, as I conceive, exolii(l<-<l the 

 exciting cause of that chemical change, which he has not inaptly described as 

 a process of fermentation, and which is the source of all volcanic and plutonic 

 phenomena. See in this connection Essays I. and VII. of the present volume. 



