THE USEFULNESS OF EARTHQUAKES. 241 



aid in the formation of shoals and banks. The larger, 

 therefore, such shoals and banks may be, the larger 

 must be the amount of land which has been washed 

 away never to reappear. And although banks and 

 shoals of this sort grow year by year larger and 

 larger, yet (unless added to artificially) they continue 

 always either beneath the surface of the water, in the 

 case of shoals, or but very slightly raised above the 

 surface. Now, if we suppose the destruction of land 

 to proceed unchecked, it is manifest that at some 

 period, however remote, the formation of shoals and 

 banks must come to an end, owing to the continual 

 diminution of the land from the demolition of which 

 they derive their substance. In the mean time, the 

 bed of the sea would be continually filling up, the 

 level of the sea would be continually rising, and 

 thus the banks would either be wholly submerged 

 through the effect of this cause alone, or they would 

 have so slight an elevation above the sea-level, that they 

 would offer little resistance to the destructive effects of 

 the sea, which would now have no other land to act upon. 

 Eut we have yet to consider the second principal 

 cause of the wasting away of the land. The cause we 

 have just been dealing with acts upon the shores or 

 outlines of islands and continents ; the one we have now 

 to consider acts upon their interior. It will, perhaps, 

 hardly be supposed that the fall of rain upon the land 

 could have any appreciable influence in the demolition 



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