Geology, as illustrated by Chemistry and Physics. 41 



tity enormous. Moreover, the flames which have actually 

 been observed appear to have been those of burning sulphu- 

 retted hydrogen, whose formation presupposes the existence 

 not of metal, but of metallic sulphurets.* 



Besides this, the assumption of the presence of these 

 metals in the interior of the earth has very little probability. 

 They could not in any case be situated in the limestone 

 strata, which for example the crater of Vesuvius has broken 

 through, nor indeed in any strata which have been formed 

 by deposition from the sea, but must be supposed to exist in 

 the primitive rocks which lie beneath all the sedimentary 

 strata. It is not my intention here to speak of other diffi- 

 culties which this hypothesis encounters. \ The celebrated 

 originator of it himself subsequently expressed a decided 

 opinion that the increase of temperature towards the interior 

 of the earth furnished a much more simple explanation of 

 volcanic phenomena. 



Wherever chemical processes attended by a development 

 of heat takes place, the products of the action are found. 

 Thus, in combustion smoke and ashes present themselves. 

 If lava had been melted by such a process, then long before 

 its flowing from the crater smoke must have issued as from 

 our furnace chimneys. Where coal strata burn as at Duttwei- 

 ler, near Saarbrucken, either melting masses of rock or heat- 

 ing them to redness, smoke ascends from fissures or through 

 the planes of stratification. Nothing of this kind is seen to 

 issue from the craters of volcanoes before the lava is poured 

 out, for the vapours which ascend from them are of a totally 

 different nature. It cannot, therefore, be subterranean pro- 

 cesses of combustion which cause the melting of lava. Now, 

 since the only other conceivable chemical process — a com- 

 bustion of the metals of the alkalies and alkaline earths — is 

 in the highest degree improbable, then, according to the 

 present state of chemical science, there remains no other 

 such process by which volcanic phenomena can be produced. 



* Naumann Lehrbuch, d. Geognosie, Bd. i., p. 123. 



t See Physical, Chemical, and Geological Researches on the Internal Heat 

 of the Globe. London, 1841, p. 297, et seq. 



