424: 0)1 Some Points in Chemical Geology. 



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 penetrating (as shown by Mr. Babbage), a 

 process which has long since ceased in the pakeozoic regions. Both 

 normal metamorphism and volcanic action are generally connected 

 with elevations and foldings of the earth's crust, all of which phe- 

 enomena we conceive to have a common cause, and to depend upon 

 the accumulation of sediments and the subsidence consequent there- 

 on, as maintained by Mr. James Hall in his theory of mountains. 

 The mechanical deposits of great thickness are made up of coarse 

 and heavy sediments, and by their alteration yield hard and resist- 

 ing 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 cur- 



[JThe notion that volcanic phenomena have their seat in the sediment- 

 ary formations of the earth's crust, and are dependant upon the combus- 

 tion 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 Erdkbrpers 7 

 in which he maintains that all crystalline non-stratified rocks, from gran- 

 ite 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 oxydizing metallic nucleus, but in known sedimen- 

 tary 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. (Naturgcschichte, vol. 1 p. 109, also Bull. Soc.GeoL 

 de France (1) vol. vii. p. 197.) 



These remarkable conclusious 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 and my own ; although in reject- 

 ing the influence of an incimdescent 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.] 



