90 Cincinnati Society of Natural History. 



times the river bed is almost dry, again it is a raging torrent. The 

 two feet of earth above the second village site, I think, has accumu 

 lated in the last one hundred and fifty years, but the three feet 

 between the layer lowest down and the second one accumulated 

 when the country was heavily wooded, and therefore was much 

 longer in forming. How long. I will not say, but it might have 

 been two hundred years. 



As to the age of Fort Ancient, it is, of course, impossible to set 

 any certain date for its erection. The only evidence that we have 

 we must draw from the timber which grows upon it and from the 

 kind of soil of which it is composed, and consider about how rapidly 

 that soil erodes. 



First. Determining the age of the timber is very .unsatisfactory ; 

 there is very little timber that can be classed as over three hun- 

 dred years old, and none that is over three hundred and fifty. The 

 present trees growing upon the bank are principally beech, poplar 

 and oak. The beech and oak are the oldest; the poplar, except in 

 the case of a few trees six feet in diameter, beins rather young. We 

 do not know how many trees flourished, decayed and fell before 

 the present generation began its growth. So we can claim only 

 three hundred and fifty years as the basis. 



The fortification is composed entirely of tough glacial and lime- 

 stone clay, which does not erode easily. Of course, it stood a 

 number of years before the timber began to grow, and the wash 

 was more pronounced those first years than during the entire cen- 

 turies that have elapsed since. When the trees started and the 

 grass commenced to grow, the roots of the vegetation would form 

 a covering and a protection which the rainfall would not affect. 



We do not draw conclusions, however, from this. The esti 

 mates are deduced from the following : When the fort was built 

 there were nearly all the ravines that there are now, but some 

 ravines have formed since. For instance, in places where there 

 w?s a level when the fort was built, there has since formed a ravine 

 or gully; this has carried out the entire wall, and has washed to the 

 depth of thirty or forty feet in three cases that I have in mind at 

 the pres?nt writing. Now, these gullies look just as old, and are 

 washed clear down to the Cincinnati limestone, as do those that 

 were in existence when the fort was completed. It must have 

 taken centuries for this tough soil to wash out, and several geolo- 

 gists who have carefully examined the structure, and who have 



