OVERLYING AND TRAP ROCKS. 129 



Occasionally there occurs a mass of trap, which in- 

 stead of being superimposed on the strata, is placed 

 laterally respecting them, or else covers, in one part, 

 the same body to which, in another, it approximates 

 in that manner. Examples of this occur in Sky and 

 in Morven ; while a careful examination shows that 

 the lateral approximation is an intersection ; so that 

 the mass is, properly, a vein. These intersecting 

 masses are often of enormous dimensions, extending 

 even for miles ; and, like the smaller veins, they 

 reach to unknown depths ; probably forming a com- 

 munication between the overlying masses and bodies 

 of similar or greater dimensions, situated beneath the 

 strata. 'That such masses do exist beneath, as well as 

 above the stratified rocks, is evinced by the circum- 

 stances often attending veins, were it not even a ne- 

 cessary inference from the general theory of their 

 origin. In these cases, the intersected and bent or 

 broken strata are also -turned upwards, as if by a 

 force acting from below ; indicating the place of the 

 parent mass and the progress of the intruding mate- 

 rial upwards. Bute presents an excellent example of 

 this fact. In Sky and elsewhere, strata are also 

 found bent over an interior or subjacent mass of trap, 

 of inaccessible depth : displaying, distinctly, what the 

 theory had inferred; while, in other instances, they 

 have been broken as well as bent, so as to have 

 given exit to the subjacent material. This particular 

 modification is obviously analogous to the cases of 

 granite, which trap resembles in so many other par- 

 ticulars ; and it has given rise to the inference for- 

 merly examined, that, in the predominant cases, it has 

 been protruded from beneath in a liquid state ; being 

 thus analogous to those products of volcanic eruption, 

 with which its mineral characters correspond so nearly, 



VOL. II, K 



