350 GEOLOGICAL APPEARANCES 



veins, the intermixture of the stratified masses with the sienite 

 remains to be accounted for, and the case seems to admit of 

 only two hypotheses. One is, That after the sienite had assu- 

 med its present form, the stratified substances were deposited 

 in the cavities of its surface. But the forms of these supposed 

 cavities, — the absence of crystals on their sides, as now exhibited 

 in the lines of junction, — the structure also of the veins, divid- 

 ing upon the sharp angles of the interjacent masses, branching 

 with every, variety of size and direction, and crossing each 

 other among the stratified masses, — all these circumstances 

 make it difficult to imagine, that the sienite would have receiv- 

 ed its present appearance, if at perfect liberty to assume that 

 which crystallisation tended to give ; and the diversities in 

 position among the stratified masses, relatively both to the sie- 

 nite and to one another, furnish the strongest objections to the 

 idea that these positions were original. This hypothesis there- 

 fore, though it has been adopted by some to explain analogous 

 appearances elsewhere, may be rejected without hesitation. 

 The hypothesis which remains, is, That the masses of gneiss, 

 limestone, &c. are portions of strata once continuous, and ]y- 

 ino- conformably with those which form the base of Ben y Gloe; 

 that these strata were bent and broken by some violent shock; 

 and that the fluid, from which the sienite crystallised, was in- 

 troduced among the fragments. 



125. Admitting this as the most probable, the nature of that 

 fluid comes immediately into question. It may be supposed to 

 have been some unknown aqueous fluid, which held the substance 

 of the sienite in solution, and deposited it by crystallisation. 

 To account for the various positions of the fragments, and the 

 height at which they are now found resting upon the main 

 rocks of sienite, it may be supposed, that the fragments fell at 

 various times from the sides of a chasm, in which the deposi- 

 tion 



