78 Dr Daubeny 07i Thermal Springs. 



the grounds on which he renounced his former views are noWhere 

 stated, and that he himself admits, in the very place in which 

 his preference for the contrary opinion is recorded, that the ex- 

 periments and observations on Vesuvius, which it was the object 

 of his memoir to detail, whilst they are inconsistent with every 

 other chemical theory of volcanos, may be accounted for on 

 this. 



The authority, therefore, of Sir H. Davy, may, I conceive, on 

 this occasion be fairly pleaded against himself, and the weight 

 of his ipse diwit in the two latter years of his life, be viewed as 

 counterbalanced by the contrary judgment he had pronounced, 

 apparently on the same evidence, at an earlier period ; neither 

 perhaps is it inconsistent with what we know of his character, to 

 suppose that he should have acquired a distaste for the theory 

 in question, when he found it seized upon and illustrated by a 

 humble class of inquirers. 



With regard to the authority of Fourier, it would be well, if 

 those who appeal to his great name in corroboration of this doc- 

 trine of a central heat, would give themselves the trouble to 

 consider what was the real scope of his celebrated memoir. They 

 would then be convinced, that the results of his analytical in- 

 quiry go no farther, than to demonstrate the compatibility of 

 such an internal heat with the phenomena presented at the sur- 

 face. The proofs, therefore, of such a cause must be sought for 

 elsewhere ; for, as we have already stated, the phenomena of 

 climate are such as may be fairly deduced from the effects of 

 solar radiation, modified by peculiarities of local situation, and 

 therefore add nothing to the evidence derived from the internal 

 temperature in favour of the existence of a central heat. 



Analysis of Professor Ehrenberg's Researches on the Irifw- 

 soria. By Meredith Gairdner, M. D. Communicated 

 by the Author. (Continued from p. 225.) With a Plate. 



III. Systematic Classification. 



The foregoing observations have no doubt prepared the mind 

 of the reader for an entire change in the distribution of this class 



