UNCLE IN ENGLAND. 241 



produced such infinitely greater changes in the 

 structure of the earth's surface than any that 

 are now going on. 



" The more you learn," he replied, i( of the 

 structure of the earth, and of the prodigious 

 thickness of the strata, which once must have 

 lain horizontally, and which have been since torn 

 up and thrown into every angle of inclination, the 

 more readily you will form an idea of the stupend- 

 ous power with which that cause must have ope- 

 rated. The changes which are now in constant 



O 



progress are very limited in their effects, and are 

 entirely confined to the surface. The action of 

 frost in crumbling the rocky tops of the moun- 

 tains ; and of rivers in carrying the fragments 

 to the sea, and thus altering the outline of the 

 coasts, I have already mentioned. Considerable 

 changes are also produced by avalanches, by 

 inundations, and by the unceasing action of the 

 waves of the sea. But these changes are slow, 

 and can never be very extensive. " The effect 

 of volcanoes is greater; and, though many 

 countries bear the traces of having been over- 

 flowed by vast torrents of lava, they are now 

 confined to a comparatively small portion of the 

 globe. But if they were far more numerous or 

 extensive, volcanoes could not have raised up or 

 overthrown the strata through which their aper- 

 tures pass, still less could they have acted upon 

 those immense regions which are not volcanic. 



