GENERAL LAWS IN GEOLOGY. 589 



sected by Faults, or fissures interrupting the strata, 

 in which the rock on one side the fissure appears 

 to have been at first continuous with that on the 

 other, and shoved aside or up or down after the 

 fracture. Again, besides these larger fractures, 

 rocks have Joints, separations, or tendencies to 

 separate in some directions rather than in others ; 

 and a slaty Cleavage, in which the parallel subdi- 

 visions may be carried on, so as to produce laminae 

 of indefinite thinness. As an example of those laws 

 of phenomena of which we have spoken, we may 

 instance the general law asserted by Prof. Sedgwick, 

 (not, however, as free from exception,) that in one 

 particular class of rocks the slaty cleavage never 

 coincides with the Direction of the strata. 



The phenomena of metalliferous veins may be 

 referred to, as another large class of facts which 

 demand the notice of the geologist. It would be 

 difficult to point out briefly any general laws which 

 prevail in such cases; but in order to show the 

 curious and complex nature of the facts, it may be 

 sufficient to refer to the description of the metallic 

 veins of Cornwall by Mr. Carne ' ; in which the 

 author maintains that their various contents, and 

 the manner in which they cut across, and stop, or 

 shift, each other, leads naturally to the assumption 

 of veins of no less than six or eight different ages 

 in one kind of rock. 



Again, as important characters belonging to the 



' Transactions of the Geol. Soc. of Cornwall, vol. ii. 



