and their Connexion with Volcanos, 77 



ducible to any fixed law, than the temperature of the interior 

 of the earth ; and Cordier himself, who founds upon it a theory 

 as to the existence of a central heat, confesses " that the differ- 

 ences between the results collected in the same place do not de- 

 pend solely upon the imperfect nature of the experiments, but 

 also upon a certain irregularity in the distribution of the sub- 

 terranean heat in different countries." 



Before, therefore, we refer the internal warmth of the globe 

 to a cause, which should imply a greater uniformity, and a less 

 anomalous distribution, than seem consistent with fact, let us 

 consider whether there are not certain causes in continual, 

 though in less regular operation, which may supply us with a 

 solution of this problem. 



We have already suggested the probability that volcanic ac- 

 tion, though most intense in certain situations and along parti- 

 cular lines of country, manifests itself likewise in a minor de- 

 gree wherever thermal or carbonated waters issue from the earth ; 

 perhaps, indeed, likewise in those spots, where accumulations of 

 carbonic acid take place, as at the bottom of neglected mines or 

 wells. This, therefore, may be one principal cause of the higher 

 temperature detected as we descend into the interior of the earth ; 

 but there are not wanting other processes, the existence of which 

 cannot be called in question, calculated to give riso to a con- 

 siderable elevation of its temperature. 



The interesting discovery of Mr Fox, with respect to the 

 electro-magnetic properties of metalliferous veins in the mines of 

 Cornwall, seems to hold out to us a completely new field of spe- 

 culation, both as to the changes that may be going on under- 

 neath, and the influence which these changes may exert upon 

 the temperature of the globe ; so that, in the absence of any 

 sufficient information on these points, it would surely be preci- 

 pitate, to pronounce upon the necessity of assuming one general 

 and equable cause, for that which may be derived from so great 

 a variety of natural processes. 



It is true, that Sir H. Davy, in one or two of his later publi- 

 cations, has shewn himself out of conceit with the theory, which 

 his own discoveries had originally suggested, and that he seems 

 to have inclined in preference to an explanation founded on the 

 doctrine of a central heat. Nevertheless, it is remarkable that 



