vii ABUNDANCE OF UNDERGROUND WATER 235 



to be heard in the distance. The nether sea, too, 

 can approach and retire ; neither of which movements 

 can take place without shock to the earth that stands 

 above it. 



VIII 



I DO not, indeed, suppose that you will long hesitate i 

 to believe that there are underground rivers and 

 a hidden sea. From what other cause could the 

 rivers burst out and come to the surface unless the 

 source of the moisture were shut up within the 

 earth ? For instance, when one sees the Tigris 

 interrupted and dried up in the middle of its course, 

 not diverted as a whole, but gradually with imper 

 ceptible, losses first lessen and then waste away, 

 where do you suppose it goes to if not to the depths 

 of the earth, especially as you see it emerge again 

 not less in volume than its former stream ? And 2 

 what are you to say when you see the Alpheus, so 

 celebrated by the poets, sink in Achaia and, having 

 crossed beneath the sea, pour forth in Sicily the 

 pleasant fountain Arethuse ? And don t you know 

 that among the explanations given of the occurrence 

 of the inundation of the Nile in summer, one is 

 that it bursts forth from the ground, and is swollen 

 not by rain from above but by water given out 

 from within the earth ? 



I have myself heard from their own lips the 3 

 story told by the two non-commissioned officers 

 sent to investigate the sources of the Nile by our 

 good Emperor Nero, a monarch devoted to virtue 

 in every form, but especially solicitous for the 

 interests of truth. The King of Ethiopia had 

 supplied them with assistance and furnished letters 



