[ 193 ] 



XXXII. Account of a Series of Experiments, showing the 

 Effects of Compression in modifying the Action of Heat. 

 By Sir James Hall, Bart. F.R.S. Lond. and Edin. 



[Concluded from -p. 157.] 



§ ix. 



Application of the foregoing Remits to Geology .—The Fire 

 employed in the Huttonian Theory is a Modification of 

 that of the Volcanoes. — This Modification must take place 

 in a Lava previous to its Eruption. — An internal Lava is 

 capable of melting Limestone.— The Effects of Volcanic 

 Fire on Substances in a subterranean and sub-marine Situ- 

 ation, are the same as those ascribed to Fire in the Hut- 

 tonian Theory. — -Our Strata ivere once in a similar Situa- 

 tion, and then underwent the Action of Fire. — All the 

 Conditions of the Huttonian Theory being thus combined, 

 the Formation of all Rocks may be accounted for in a sa- 

 t isfactory Manner. — Con clus ion . 



XIaving investigated, by means of the foregoing experi- 

 ments, some of the chemical suppositions involved in the 

 Huttonian theory, and having endeavoured to assign a de- 

 terminate limit to the power of the. agents emp'oyed, I shall 

 now apply these results to geology, and inquire how far the 

 events, supposed antiently to have taken place, accord with 

 the existing state of our globe. 



The most powerful and essential agent of the Huttonian 

 theory is flic, which I have always looked upon as the same 

 with that of volcanoes, modified by circumstances which 

 must, to a certain degree, take place in every lava previous 

 to its eruption. 



The original source of internal fire is involved in great ob- 

 scurity ; and no sufficient reason occurs to mc for deciding 

 whether it proceeds by emanation from some vast central 

 reservoir, or is generated by the local operation of some che- 

 mical process. Nor is there any necessity for such a deci- 

 sion ; all we need to kno'.v is, that internal fire exists, which 

 ii<» one can doubt, who believes in the eruptions of Mount 



Vol. 25. No. Q9, Aug. 1906. N Vesuvius, 



