THE USEFULNESS OF EARTHQUAKES. 243 



Combining the effects of the sea's action upon the 

 shores of continents, and of the action of rain upon 

 their interior, and remembering that unless the process 

 of demolition were checked in some way, each cause 

 would act from year to year with new force one 

 through the effects of the gradual rise of the sea-bed, 

 and the other through the effects of the gradual increase 

 of the surface of ocean exposed to the vaporizing action 

 of the sun, which increase would necessarily increase 

 the quantity of rain yearly precipitated on the land 

 we see the justice of the opinion expressed by Sir John 

 Herschel, that, " had the primeval world been con- 

 structed as it now exists, time enough has elapsed, and 

 force enough directed to that end has been in activity, 

 to have long ago destroyed every vestige of land" 



"We see, then, the necessity that exists for the action 

 of some restorative or preservative force sufficient to 

 counteract the effects of the continuous processes of 

 destruction we have indicated above. If we consider, 

 we shall see that the destructive forces owe their effi- 

 ciency to their levelling action, that is, to their influence 

 in reducing the solid part of the earth to the figure of 

 a perfect sphere ; therefore the form of force which is 

 required to counteract them is one that shall tend to 

 produce irregularities in the surface-contour of the 

 earth. And it will be remarked that, although up- 

 heaval is the process which appears at first sight to be 

 the only effectual remedy to the levelling action of 



