80 AN ENQUIRY INTO THE NATURE OF [Ch. XIII. 



these details does not so satisfactorily point to the same con- 

 clusion ; though it affords indications that the trap-rocks are 

 sometimes accompanied by highly inclined strata, after the 

 manner of the primary unstratified masses. If, however, we 

 extend the comparison between trap and granite, it will be 

 found that, although some points of resemblance exist, there 

 are some of a very different character; and none more so 

 than the mode of the arrangement of the strata adjacent to 

 these rocks, the subject now under consideration. 



The strata which surround granite are generally highly 

 inclined, often dipping for many miles in a uniform direction, 

 and sloping on either side from the central rock, which thus 

 forms a ridge or anticlinal axis. They are supposed to have 

 been elevated from a horizontal position by the protrusion of 

 granite in a fluid or solid state, effected by the expansive 

 agency of the central fire. 



It has not, however, been satisfactorily demonstrated that 

 the central fire can operate in this manner ; but it has been 

 shown that it is capable of elevating whole continents, in 

 which case the strata generally suffer no disturbance, hills 

 and valleys retaining their previous relations : and surely a 

 power adequate to produce such vast effects, might have been 

 expected to elevate the strata into inclined positions, if such 

 were the usual mode of its operation. 



For the sake of argument, let it be admitted that the gra- 

 nite, in a fluid state, has tilted up the strata : and that the 

 latter were in a state of semi-fusion, or not, according as the 

 supposed contortions of these rocks require a degree of duc- 

 tility. Could horizontal strata be elevated to considerable 

 angles, and even into a perpendicular position, without sus- 

 taining cracks and fissures ? If not, how came it to pass that 

 these attenuated, if not fissured, strata could, contrary to all 

 known laws, oppose a force capable of protruding a mass of 

 granite many leagues in diameter ? In the cases of mines in 

 warfare, of blasting of rocks, or of the bursting of steam- 

 boilers, if a breach of continuity be once effected, an explo- 



