ON GRANITE. C 2 l 23 



The late Dr. Hutton of Edinburgh has given us a very dif-. Dr. Hutton con- 

 fcrent geological view of granite from that contained in the £*£" s r * mi * 

 preceding pages. In my outline of the mineralogy of the 

 Scottifti ifles, I endeavoured to fliew the fallacy of Dr Hut- 

 ton's opinions. Profeffor Playfair, however, in his illuftra- 

 tions of the Huttonian theory lately publifhed, has ftated a 

 number of fafts, which he coniiders as fully confirming Dr. 

 Hutton's ideas refpe&ing granite. I therefore take this op- 

 portunity to ftate, more fully, the reafons that incline me to 

 differ intirely from thefe gentlemen. 



Profeffor Playfair is of opinion, that the diftindion of granite p ro feflbr Play- 

 into different formations is hypothetical. To this I can by no fair ' s opinion 

 means affent ; on the contrary, I am fully convinced, that the in g diftincYions" 

 granite formations are well afcertained, and this will be evi- are hypothetical, 

 dent from the following obfervations : it is a polition, the The order of 

 truth of which is acknowledged by every geognoft, that of date in granite 

 two feries of rocks, the neweft, is that which covers the [j^ted from'^heir 

 other. The Greifenftein granite formation lies over the primi- filiations. 

 tive Hate, and is consequently newer than the old granite, 

 gneifs, mica Hate, and primitive flate. To rende rthis intelli- 

 gible to thofe unacquainted with the Wernerian geognofie, I 

 have reprefented this formation in the (ketch, Fig. 1. Plate 

 XIII. 



From this fketch it is plain, that after the depofition of the 

 old granite, gneifs, mica flate, and primitive flate, the water 

 had again rifen, and depoiited over the ends of thefe ftrata, 

 this newer granite formation. 



The fienite formation, which has been often confounded with sienite ftyii v 

 the old granite, lies over the four older primitive formations, tion. 

 and has, interpofed, a layer of breccia, compofed of fragments 

 of thefe rocks. This demonftrates, as we have already re- 

 marked, that the water muft have rifen and depofited firft the 

 fragments of the older flrata, (which it had tore off in its ri- 

 sing) and upon this the fienite. The fketch illuftrates, thele. 

 appearances, Fig. 2, Plate XIII. 



Thefe facts and explanations, which are drawn from the 

 Wernerian geognofie, I fliall now contrail with thofe of Dr. 

 button, and Profeffor Playfair. 



Profeffor Playfair remarks, p. 309. " Veins of granite are Remarks of 

 alfo frequent in Cornwall, where they are known by the name Profeffor Play- 

 ^ lodes, the farne name which is, applied in that country Mrf^fc/ki 



metallic Cornwall. 



