1S13# -] On Transition Rocks. 1° 5 



Hutton applied the term alpine scMsfus in such a way as » to 

 leave us quite uncertain with respect to the species of rock he 

 meant." And this is far from being the only instance that might 

 be easily adduced, not only from his writings, but also from those 

 of more recent philosophers of the same school. 



Mr. A. justly observes, that the geognostic system of Werner 

 is divided into three great classes, the primitive, transition, and 

 floetz roeks,-proposes '< to notice particularly the class of locks 

 named transition," and to show « that they are of an older date 

 than the granite which maintains the first place in po.nt ot 

 priority in the system of Werner." How far he has been able to 

 succeed in making out this last position will presently appear. 



After telling us that he takes his ideas of the Wernenan 

 geognosy from the third volume of Professor Jameson s Mine- 

 ralogy (and we allow that he cannot take them from a better 

 source, h being, as he justly states, "the ^^ennc.c. 

 count we have of the system taught at Fieyberg ; ) after, 1 say, 

 telling us this, giving us the definition of grey-wacke, and the 

 other rocks constituting the transition class with a sketch of 

 their geographic distribution in the islands of Great Britain and 

 Ireland, Mr. Allan proceeds to inform us, that he made a 

 tour last summer through Cornwall and Devonshire, and there 

 found that the Wernerian geognosy would not apply. He 

 knew, he says, that granite abounded in the Stannaries, and 

 that tin and wolfram occurred in it ; and as these metals 

 (according to his view) never do occur but in the oldest granite, 

 therefore the granite of Cornwall must be the oldest Here, 

 « therefore, he expected to find a perfect epitome of the VVer- 

 ne.ian system, containing the usual series of pr.mitive rocks, 

 descending from granite through gneiss, mica-slate, and clay- 

 slate, with all the et cceteras of serpentines, traps, and porphy- 

 ries but in this he was mistaken." Certainly he was mistaken 

 but in a very different way from that in which he conceived 

 himself to be. Let us see what Professor Jameson, in his tAe- 

 ments of Geognosy (the work which Mr Allan constantly refers 

 to), says with respect to the occurrence of tin and wolfram. In 

 treating of tin, he tells us that it occurs in very old veins that 

 traverse granite, gneiss, mica-slate, and clay-slate; that ,t occurs 

 disseminfted through granite, and in beds that at ernate W , h 

 that rock. He adds, that the granite appears to be long to the 

 newest formation. (El. of Geognosy, p. 2610 '>t P'j*™?* 

 the same work, in the tabular view, the Professor gives us again 

 the geognostic situation of tin, and the only granite mentioned 

 Utile 'newest. Of wolfram, he says, at p. 261, that it .occur, 

 in veins both in primitive and transition mountains. And again, 

 at p. 811, in the tabular view, wolfram il stated as occurring 

 not in the oldest, but only in the newest granite formation. 



