CHAP. III. ANCIENT MOUNDS OF VALLEY OF THE OHIO. 39 



to a certain depth in mud, as at Memphis and Heliopolis, is 

 the era when the city fell into such decay that the ancient 

 embankments were neglected, and the river alloAved to in- 

 undate the site of the temple, obelisk, or statue. 



Even if we knew the date of the abandonment of such 

 embankments, the enclosed areas would not afford a favor- 

 able opportunity for ascertaining the average rate of deposit 

 in the alluvial plain ; for Herodotus tells us that in his time 

 those spots from which the Nile waters had been shut out 

 for centuries appeared sunk, and could be looked down into 

 from the surrounding grounds, which had been raised by the 

 gradual accumulation over them of sediment annuallj'^ thrown 

 down. If the waters at length should break into such de- 

 pressions, they must at first carry with them into the enclosure 

 much mud washed from the steep surrounding banks, so that 

 a greater quantity would be deposited in a few years than 

 perhaps in as many centuries on the great plain outside the 

 depressed area, where no such disturbing causes intervened. 



Ancient Hounds of the Valley of the Ohio. 



As I have already given several European examples of 

 monuments of pre-historic date belonging to the recent 

 period, I will now turn to the American continent. Befoz*e 

 the scientific investigation by Messrs. Squier and Davis of the 

 "Ancient Monuments of the Mississippi Valley,"* no one 

 suspected that the j^lains of that river had been occupied, for 

 ages before the French and British colonists settled there, by 

 a nation of older date and more advanced in the arts than 

 the Eed Indians whom the Europeans found there. There 

 are hundreds of large mounds in the basin of the Mississippi, 

 and especially in the valleys of the Ohio and its tributaries, 

 which have served, some of them for temples, others for out- 



* Smithsonian Contributions, vol. i., 1847. 

 4 



