234 PHYSICAL SCIENCE BK. vi 



in the place where all waters are. The earth would 

 not be able to produce so many rivers unless it 

 poured them from a copious reserve. 



4 This being so, sometimes below the earth a 

 river must become swollen, and leaving its banks 

 assail with violence all obstacles that meet it. So 

 there will be a movement of some point on which 

 the river has made an onset, and which it will keep 

 lashing until its waters fall. Or it may happen that 

 the constant wear of a stream may eat away 

 some quarter, dragging down thereby some mass 

 above, by whose fall, in turn, the surface which 



5 rested on it is shaken. Now surely a man trusts 

 too much to the sight of the eyes and cannot launch 

 out his imagination beyond, if he does not believe 

 that the depths of earth contain a vast sea with 

 winding shores. I see nothing to prevent or oppose 

 the existence of a beach down there in the ob- 

 scurity, or a sea finding its way through the hidden 

 entrances to its appointed place. There, too, it 

 occupies as much space as here, perhaps more, 

 since the regions up on earth have had to be shared 

 with so many living creatures ; but the hidden 

 regions being desert without inhabitant give freer 



6 scope to the waves of the nether ocean. And who 

 is there to hinder the sea from swelling there and 

 being tossed by all the winds that every interstice 

 of the earth,; and every species of atmosphere can 

 create ? So, then, when a storm greater than ordi- 

 nary has arisen, it may beat upon some one side of 

 the earth with too great vehemence and move it. 

 For on the surface likewise, many places which 

 had been far from the sea have felt the violence of 

 its sudden approach : villas almost out of sight of 

 it have been invaded by the waves which used only 



