Ch. XIII.] THE INCLINED POSITIONS OF STRATA, 281 



sion immediately follows: so we should expect the same to. 

 take place if the incumbent strata were broken through by 

 granite under the circumstances just specified ; and, the fluid 

 granite having found a vent, the strata, freed from the pres- 

 sure, would fall back into their original position. 



In the contemplation of the effects of a force much inferior 

 to that just considered, viz. the production of elevation-craters, 

 as propounded by Von Buch, Lyell argues against the proba- 

 bility of such an elevation, and concludes with the following 

 observation : "Is it possible to conceive that elastic fluids 

 could break through a mere point, as it were, of the earth's 

 crust, and that, too, where the beds were not composed of soft 

 yielding clay, or incoherent sand, but of solid basalt, thou- 

 sands of feet thick, and that they would inflate them, as it 

 were, in the manner of a bladder ? Would not the rocks, on 

 the contrary, be fractured, fissured, thrown into a vertical 

 position ; and, ere they attained the height of seven thousand 

 feet, would they not be reduced to a mere confused and 

 chaotic heap ? " * How much more, then, ought we to expect 

 that the protrusion of immense masses, many leagues in 

 diameter, amongst the strata, so as to raise them to a con- 

 siderable angle over immense tracts of country, could not be 

 effected without producing cracks and fissures : and if this 

 happened, that is, if the internal elastic force overcame the 

 incumbent resistance, how could these strata escape total 

 destruction ? 



Some attempt to get over this difficulty by supposing that 

 the granite was sometimes protruded in a solid state ; but the 

 almost universal occurrence of granite-veins penetrating the 

 slate, appears to be in favour of the opinion which considers 

 the granite to have been in a state of fusion during such 

 catastrophes. 



It has been before stated that Sedgwick and Murchison 

 have been induced to conclude that the granite of Arran, 



* Principles of Geology, vol. i, p. 389* 



