288 Reply to Jlir. Allan's Olservatiom [Aphie, 



Jameson's third volume, p. lOK, where he will find it described as 

 resting on gneiss. 



Mr. Allan refers back to Professor Jameson's second volume, 

 publislied in 1805, where, speaking of tin, the Professor says: 

 *' it occurs only in primitive rocks as granite, gneiss, &c. ; and in 

 the oldest of all the metals." Such, no doubt, was his opinion in 

 1805; but subsequent observations must have induced him to alter 

 it: and in 1808, when his third volume was published, to consider 

 tin as occurring not only in primitive but also in transition rocks. 

 Thus then it appears that the newest granite is that which contains 

 the tin and wolfram. I do not " reduce the age of these to the 

 period of the transition series ;" I only say that tin and wolfram 

 occur in granite, gneiss, mica-slate, and clay -slate, and sometimes 

 in transition rocks; and that the granite is "of the newest formation. 

 But even allowing that these metals occurred in the oldest as well 

 as in the newest granite, nothing would thereby be added to the 

 strength of Mr. Allan's argument. For if they are found in both 

 kinds of granite, their presence in that of Cornwall can never 

 prove it to be the oldest. Neither can this circumstance of itself 

 prove it to be the newest. But Mr. Allan admits that the Cornwall 

 granite contains fragments. Now the essential character of new 

 granite is its containing fragments. Mr. Allan seems to think that 

 I was not entitled to put the question, '' Who ever heard of frag- 

 ments being found in the first granite formation ?" and replies, 

 " All I have in answer to say is, that the granite of Cornwall pre- 

 senting the characters of the most ancient cavities of that rock, 

 according to the authority of Werner himself, as given by Pro- 

 fessor Jameson, does contain, in the veins which extend from it, 

 abundance of fragments." 1 answer that it has then the character 

 of the newest, not of the oldest granite ; for tliis Cornish rock, it 

 seems, contains tin and wolfram along with fragments ; and these 

 two circumstances conjoinsd, characterize the newest granite. 



Mr. Allans opinion respecting conglomerated rocks signifies but 

 little. The fact is that according to Werner such rocks do occur 

 in primitive country. Mr. Allan may call them by a different 

 name if he chooses. 



The only example he produces of the killas, as he chooses to call 

 it, resting immediately on the granite, is at St. Michael's Mount; 

 and there we are told by him, that it is a fine-grained gneiss, or at 

 least has all the " appearance" of it. Now in the account of 

 Werner's transition rocks, as given by Professor Jameson, no such 

 rock as this is mentioned. Fine-grained gneiss is not among the 

 number. And hence I repeat that I am, in fair inference, still 

 entitled to maintain, that the killas of St, Michael's Mount, the 

 only variety seen immediately resting on the granite by Mr. Allan, 

 belongs not to the transition series of Werner, as given by Pro- 

 fessor Jameson, and referred to by Mr. Allan. He has not there- 

 fore made out his first position. Neither can we admit the second j 



