Ch. XL] THE PRIMARY ROCKS. 217 



truded in a sold form through the adjacent oolitic deposits ; 

 and, in the mechanical violence, indicated by the fractured 

 and dislocated state of the stratified rock ; and in the occur- 

 rence of a breccia composed of fragments both of granite and 

 oolite, they find confirmation of their views. 



In short, the prevailing geological theory is that of Hutton ; 

 modified indeed, and improved on, so as to adapt it to the 

 numerous and important facts that have been collected since 

 his day. One of the arguments which he triumphantly ad- 

 vanced against his opponents, the Wernerians, was founded, 

 on the penetration of the stratified rocks by granitic veins, 

 proceeding from the main mass of this rock ; and likewise, 

 on the occurrence of angular pieces of slate, enveloped in the 

 granite ; and other apparent signs of confusion and violence, 

 which are generally found at the junction of the stratified and 

 unstratified rocks. These facts are still esteemed, as afford- 

 ing an impregnable position for the Plutonic doctrine; and, 

 though the followers of Werner have gradually submitted, 

 yet the Huttonians are continually adding outworks to this 

 strong-hold, in the hopes of increasing its security. This 

 measure, however, has created more points that require to be 

 protected; and, as has often been the case, this extended 

 line of defence may ultimately cause its surrender. But to 

 drop the simile, let us ask whether analogy has not been car- 

 ried too far in this matter ? It does not follow, because in 

 volcanic formations we find one mass of lava penetrating the 

 hollows and fissures of a former lava- stream, or of the ad- 

 jacent stratified rocks; nor, because cracks and fissures in 

 the volcanic cone are filled with sublimated matter ; it does 

 not follow, because such is the condition of these regions, that 

 primary districts have been subject to similar catastrophes : 

 and yet many geologists have not only referred the formation 

 of granite- veins to an internal igneous agency, but also sup- 

 pose that all the mineral and metalliferous veins which 

 traverse the primary rocks, have had the same origin ; fissures 

 having been first formed, and subsequently filled from be- 



