Br. T. Sterry Sunt — On Volcanic Action. 247 



has not been sufficient for its entire solidification, is, however, not so 

 probable. Such a crust on the cooling superficial layer would, from 

 the contraction consequent on the further refrigeration of the liquid 

 stratum beneath, become more or less depressed and corrugated, so 

 that there would probably result, as I have elsewhere said, "an 

 irregular diversified surface from the contraction of the congealing 

 mass which at last formed a liquid bath of no great depth, surround- 

 ing the solid nucleus." Greological phenomena do not, however, in 

 my opinion afford any evidence of the existence of yet unsolidified 

 portions of the originally liquid material, but are more simply 

 explained by the third hypothesis. This, like the last, supposes the 

 existence of a solid nucleus, and of an outer crust, with an interposed 

 layer of partially fluid matter, which is not, however, a still unsoli- 

 dified portion of the once liquid globe, but consists of the outer part 

 of the congealed primitive mass, disintegrated and modified by 

 chemical and mechanical agencies, impregnated with water, and in a 

 state of igneo -aqueous fusion. 



The history of this view forms an interesting chapter in geology. 

 As remarked by Humboldt, a notion that volcanic phenomena have 

 their seat in the sedimentary formations, and are dependent on the 

 combustion of organic substances, belongs to the infancy of geology. 

 To this period belong the notions of Lemary and Breislak {Cosmos, 

 V. 44:3; Otte's translation). Keferstein in his Naturgeschichte des 

 ErdJcorpers, published in 1834, maintained that all crystalline non- 

 stratified rocks from granite to lava, are products of the transforma- 

 tion 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 in an oxy- 

 dizing metallic nucleus (Davy, Daubeny), but in known sedimentary- 

 formations, where they are the result of a peculiar kind of fermenta- 

 tion, which crystallizes and arranges in new forms the elements of 

 the sedimentary strata, with an evolution of heat as a result of the 

 chemical process {Naturgescliichte, 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 incandescent 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 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 



