37 



lagous to the divisional planes which alike penetrate plutonic rocks and the strata above them 

 usually in directions approaching to vertical, and which also exist in gneiss, but to those beds 

 in granite which von Buch considers as always conforming to the external surface of the 

 granitic bubble, of whatever form that may te, and which Sir H. de ia Beche describes as 

 being in Devonshire and Cornwall actually parallel to the strata of superjacent sedimentary 

 rocks where the plane of contact can be seen (1). 



for it would destroy the melamorphic theory also. The Treatise on Geology was published in 1837, and the 

 second edition of Mr. Lyell's Elements in 1841 , but in noticing some objections to the metamorphic theory Mr. 

 Lieix does not allude to Professor Phiixips' argument. It is to be presumed therefore that he discredits the 

 fact on which it rests , and as I do not fiiul it mentioned by Prof. Ja mes os , who has studied gneiss carefully, 

 nor by other wrifers, we raust wait for further invesligation. Professor Jamesojt, on the contrary, in Mekbai's 

 Encyclopaedia of Geography published in 1834 (p. 219) positively states that the concretions of limestone , gneiss, 

 mica -sla Ie and other rocks of the priraitive class have the same characters as those of granite i. e. »they are joined 

 together without any basis or ground , and at their line of juncture are eithor closely attached together or ara 

 interniixed ," and frequently branches of the one concretion shoot into the other or the concretions mntually ira- 

 press each other. 



(1) The study of plutonic rocks and of mineralogy appears to have been somewhat neglected by geologists of the 

 English school, and, making due allowauce for the inftuence of "Werseb's theories, I should be disposed to gire 

 much weight to the inferences of the Scotlish geologists who, animated by the ardour first kindled *X[Freyberg, 

 during many years laboriously and minutely explored the mountains , coasts and islands of their native country. 

 Gneiss is largely developed in the north of Scotland and frequently associated with granite , and the analogy be- 

 tween them must be very strong to admit of Professor Jamesos declaring that »granite occurs in masses , often 

 many miles in extent , surrounded by gneiss , mica- slate , and clay - slate , and so connected with these rocks, 

 that the whole may be considered as the result of one grand process of crystallization ; that is , the granite is of 

 contemporaneous formation with the gneiss as the gneiss is with the super -imposed mica -slate, and the mica - slate 

 again wilh the clay- slate which rest uponit. In other instances the granite alternates in beds , often of enor- 

 mous magnitude , with gneiss , mica - slate , clay - slate , and other pritnitive rocks, or it traverses these in 

 the form of veins." Again , »granite is sometimes disposed in great beds in gneiss and other rocks, and ocea- 

 sionally these beds appear divided into strata. In other instances , in granite mountains we observe besides the 

 tabular, globular and other structures , also the stratified ; but this lalter is, in general, less perfect than what 

 is observed in gneiss and other rocks". It is true Professor Jamesoü then believed in the Wernerian theory 

 (which he has since largely abandoned , for in his latest classitication he distributes the hypogene rocks into Plu- 

 tonian and Neptunian) but he would not misrepresent facts , and the facts which he observed in Scotland seemed 

 to him lo demonstrate the derivation of granite and gneis frora a common origin. Now this conclusion is quite 

 geparable from the ulteriour speculation as to the nature of the origin , and in the present advanced state of our 

 knowledge it seems to require us to substitule a plutonic for an aqueous , without the intervention of the metamor- 

 phic , theory. Let me not be understood however as desirous of embracing a direct plutonic theory in the place 

 of the metamorphic. All I maintain is that there is a limit where it ceases to be a theory and hecomes an hypo- 

 thesis, and this limit is narrow compared wilh the vast province over which its leading exponents extend it. As 

 an hypothesis it is highly valuable , having already guided investigations which have been rich in results. lts le- 

 gitiraate domain , of which the boundaries are defined by geological demonstratiou , is constantly enlarging ; and, 

 in the present palmy condition of the science , we may hope that geologists, in a few years, will be able to 

 determine whether the bulk of what are termed the primary or hypogene stratified rocks be semi- plutonio (i. e. 

 metamorphic) or enlirely plutonic , in the same sense in which granite is. 



At the present day it is not so much dogmalism , prejudice or a reck'ess spirit of speculation in men, that maintams 

 riyal theories in geology , as that higher metamorphic power of nature which is ever reproducing the elements of 



