Theory of Central Heat. 517 



which such a theory applies to the explanation of a multitude of phys- 

 ical phenomena which cannot be here detailed, certainly strengthens 

 the conviction of its truth. 



It is hut a few years since this theory was formally developed in 

 the sientific world ; and although it was viewed by many as the very 

 extravagance of hypothesis, yet it is interesting to see how very rap- 

 idly it has gained credence. Nor can this fact be explained without 

 admitting that it carries with it strong marks of truth. The state of 

 opinion on this subject among European geologists, may be learnt 

 from the following paragraph of a recent able French writer on Vol- 

 canoes. " If" says he, " I have dwelt long on the ideas of Cordier, 

 it is because they are now professed by the most illustrious geologists 

 of our age. They rest, moreover, on facts so numerous and so well 

 established, that it is impossible not to regard them as a faithful rep- 

 resentation of what must have happened at the commencement of 

 things, and of what is now taking place. The hypothesis of central 

 heat, and by consequence that which imputes the origin of volcanic 

 matters to a fiery mass in the interior of the globe, may be placed in 

 the rank of truths the most firmly established. In proportion as ob- 

 servations multiply, this hypothesis is confirmed : the small number 

 of phenomena yet involved in some obscurity, will be explained more 

 easily than those which have been brought to light before : and the 

 systematic minds which still resist the evidence, will soon find them- 

 selves compelled to abandon their opinions, which have already fallen 

 into the most profound discredit."* 



" As to the central heat" says Dr. Macculloch, " if there is not am- 

 ple proof of this, I know not that geology can furnish proof of any 

 thing," &c. f 



Even the chemical theory of volcanic action, which imputed it to 

 the oxidation of the metalloids, and which seemed a few years ago to 

 be enlisting able advocates in its defence, appears in Europe to be 

 nearly abandoned. Even Sir Humphrey Davy, who originally pro- 

 posed it, subsequently abandoned it ; and says that "the hypothesis of 

 the nucleus of the globe being composed of fluid matter, offers' a still 

 more simple solution of the phenomena of volcanic fires than that 

 which has been just developed."! His surviving brother Sir John 

 Davy, however, still defends the chemical theory, as does also Profes- 

 sor Daubeny. 



* Considerations sur les VoJcans &c. par M. J. trirardin, Paris 1831, p. 152. 



T System of Geology, Vol. 2, p. 408. 



t Philosophic-Hi Transactions for 1828. Part 1. 



