GEOLOGY. 311 



The almost constant presence of remains of infusorial animals in volcanic 

 products, as observed by Ehrenberg, is evidence of the interposition of fos- 

 siliferous rocks in volcanic phenomena. 



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 

 sediments, the temperature, and the depth to which they are buried: while 

 the unstratificd nucleus of the earth, which is doubtless anhydrous, and, ac- 

 cording to the calculations of Messrs. Hopkins and Hennesey, probably solid 

 to a great depth, intervenes, in the phenomena under consideration, only as 

 a source of heat.* 



VIII. The volcanic phenomena of the present day appear, so far as I am 

 aware, to be confined to regions covered by the more recent secondary and 

 tertiary deposits, which we may suppose the central heat to be still penetrat- 

 ing (as shown by Mr. Babbage), a process which has long since ceased in 

 the palaeozoic regions. Both normal metamorphism and volcanic action are 

 generally connected with elevations and foldings of the earth's crust, all of 

 which phenomena we conceive to have a common cause, and to depend upon 

 the accumulation of sediments, and the subsidence consequent thereon, as 

 maintained by Mr. James Hall in his theory of mountains. The mechani- 

 cal deposits of great thickness are made up of coarse and heavy sediments, 

 and by their alteration yield hard and resisting rocks ; so that subsequent 

 elevation and denudation will expose these contorted and altered strata in 

 the form of mountain-chains. Thus the Appalachians of North America 

 mark the direction and extent of the great accumulation of sediments, by 

 the oceanic currents during the whole palaeozoic period; and the upper por- 

 tions of these having been removed by subsequent denudation, we find the 

 inferior members of the series transformed into crystalline stratified rocks. t 



* The notion that volcanic phenomena have their seat in the sedimentary for- 

 mations of the earth's crust, aud 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 maintains that all crystalline non-strat- 

 ified rock, 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 be- 

 tween 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 elements of the sedimentary strata, with evolution of heat as an 

 accompaniment of the chemical process. Naturgeschichte, vol. i. p. 109; also Bull. 

 Soc. Gcol. df- 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 writers. 

 They are, as will be seen, in many respects, an anticipation of the views of Herschel, 

 aud my own ; although in rejecting the influence of an incandescent nucleus as a 

 source of heat, he has, as I conceive, excluded 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 my 

 paper on the Theory of Igneous Rocks and Volcanoes, in the Canadian Journal for 

 May, 1858; see also Annual Sci. Dis., 1860. 



t The theory that volcanic mountains have been formed by a sudden local ele- 

 vation or tumefaction of previously horizontal deposits of lava and other volcanic 



