136 ON THE CHARACTERS AND DISPOSITION 



subject will be found in the history of that rock; but 

 I may here remark, that it is chiefly by the passage 

 of veins from a mass of granite through the incumbent 

 strata, that its relative posteriority to these is indicated. 

 It would be attempting to demonstrate a self-evident 

 proposition, to say, that of two coexisting rocks, of 

 which the one traverses the other, the traversing body 

 is the latest in origin. TJhat such a vein is a prolon- 

 gation from a mass of granite, renders the posteriority 

 of the latter equally an axiom. 



Judging by this criterion, a given mass of granite 

 is posterior in origin to every stratum in a series 

 which is traversed by its veins, or, what is equivalent, 

 is disturbed by its contiguity. Mere contiguity with- 

 out disturbance will not prove it; as strata might be 

 deposited on granite, and as it is elsewhere shown 

 that they have actually been so deposited. But al- 

 though this defines the highest limit of relative an- 

 tiquity, it leaves the lowest indefinite; since, in a deep 

 series of strata, the superior, or distant, portions may 

 have been but slightly disturbed, or have entirely 

 escaped disturbance by a granite which has not emitted 

 its veins far beyond its immediate boundary. How- 

 ever certain therefore it may be, that any mass of 

 granite is posterior to the gneiss, the micaceous schist, 

 or the argillaceous schists which it traverses, or into 

 which it intrudes, we are unable to prove that it is 

 not also posterior even to the secondary strata that 

 lie above them, except in those cases already men- 

 tioned where the actual contact is visible. If there- 

 fore the elevation of the primary strata from the hori- 

 zontal to the inclined position is to be attributed to 

 the formation of granite, there is no absolute proof 

 to be drawn, from the nonexistence of that rock 

 among the secondary strata, that these also have not 



