268 ON THE TRANSMUTATION OF ROCKS, &c., 



Mint, Mr. Stephens and Mr. Krefft, have all at some time or 

 other studied on the spot the examples I propose to dwell on from 

 our own vicinity. 



I must not, however, confine myself to them alone, for if they 

 are to be explained, it can only be by comparison with other 

 instances of like kind in other countries. 



The terms Transmutation and Transmuted are equivalents of 

 Metamorphism and Metamorphic ; but I incline to the Latin 

 rather than to the Greek derivatives, because it seems to me they 

 are more expressive of what is intended. They occur very often 

 in geological treatises, and one class of ancient formations is 

 especially called " metamorphic," because they are exposed over 

 wide areas, and exhibit everywhere the evidence of the trans- 

 mutations they have undergone in deep recesses of the earth's 

 surface before they were brought up and visibly exposed. It is 

 not of these formations that I propose to treat, except in a passing 

 way, on this occasion. But on other instances of change induced 

 in rocks of other formations under circumstances and conditions 

 which appear explanatory of the causes of change, I may dwell 

 longer. 



It may seem a strange thing to some, to have it propounded 

 that there is nothing really stable in the solid structure of the 

 earth's surface. 



Observation shows that in rocks of all ages there have been 

 external and internal changes, either of composition or of texture, 

 which must have gone on in some of them from the beginning, 

 and, therefore, it is reasonable to infer in all ; and these changes 

 can also be proved in some instances to be now in progress. I 

 am not speaking of rocks in the act of formation, though Trans- 

 mutation may be contemporaneous with deposits from the very 

 first ; but I assume that the deposits have taken place, and that 

 the transmutations of them have been of subsequent date. 



It has been observed in numerous localities that at the contact 

 of two rock formations, both of them have undergone a change of 

 material or of composition or of texture. This is most frequently 

 the case where one formation belongs to sedimentary or aqueous 

 rocks, and the other to what are called igneous. 



In some instances, the alteration seems to be induced by what 



