Crystalline Silicide Slates. 166 



Let us now turn to the other party, viz., to those who re- 

 cognise the reality of the transmutations. The mistake com- 

 mitted by these geologists, in not, above all things, bringing 

 forward simply and solely the ascertained truth itself, has been 

 already alluded to. Owing to this error, the general reception 

 of this truth into science has been refused ; and notwithstand- 

 ing that care had been taken just to render it agreeable to 

 chemists, by means of attempts at explanation which were 

 added, nothing was obtained from them but an admonitory 

 lecture, of which a repetition has been given above. By 

 adopting heat as the chief agent in the transmutations, it was 

 expected to satisfy the chemists ; and I shall here limit my 

 observations to this circumstance, that the conversion-phe- 

 nomena are in this manner brought under volcanism. 



None of the facts relating to this question are in favour of the 

 opinion, and many are against it, that heat has been in operation 

 in the conversion of various uncrystalline rocks into gneiss, 

 hornblende-slate, &c. In so far as the transmutations have 

 taken place, where the altered strata meet with certain bound- 

 ing foreign masses, no case has yet been met with, which 

 shews, as a matter of fact, that such masses have produced the 

 change in consequence of their having been in a very hot con- 

 dition. It is but pure and mere hypothesis when it is asserted 

 that the rocks here spoken of were in a hot liquid state ; and 

 even though they had been so, it is far from being a necessary 

 consequence that the change was effected at that time. I have 

 previously directed attention to this point ; and I have also 

 already stated that, moreover, there are circumstances con- 

 nected with the contact- changes which really positively prove 

 that heat did not operate in causing these transmutations. 



Those gneisses, mica-slates, talc-slates, &c., that are not at 

 all in contact with the unstratified rocks, near which, generally, 

 meeting strata of different slates are seen to be crystalline, 

 seem best adapted for disproving the idea that the change 

 by which they received their crystalline structure was pro- 

 duced by the aid of a very high temperature. In order to 

 shew whence the great heat came, the most arbitrary hypo- 

 theses are had recourse to, but even these fail. When 

 whole countries, from the surface to the greatest depths, are 



