GEOLOGY, 195 



These slate rocks are in some places fifty feet 

 high, and have been worn away in several places 

 more than eighty rods ; and as this operation has 

 been carried on with a steady progression, there 

 might perhaps be some means discovered of as- 

 certaining the time of the process. It is supposed 

 that a probable datum might be obtained by ex- 

 amining a number of the trees which grow in a 

 thin layer of earth on these rocks, and which have 

 been undermined by the rock failing off. Losing 

 their support and nourishment on that side, they 

 die, while the other side is supported and nourish- 

 ed, and continues to live and grow. By in- 

 specting a number of trees in this situation, 

 and ascertaining their age by the concentric cir- 

 cles since they lost their support, and comparing 

 that with the extent of the wearing away of the 

 rock since that period, a pretty accurate measure- 

 ment of the time of this operation might be es- 

 tablished. Of the certainty of this process there 

 is the most unquestionable evidence. Near the 

 Eighteen Mile Creek, about fifteen miles from 

 Buffalo, a thin bed or sheet of lime stone appears 

 in a high perpendicular ledge of slate. It is 

 about a foot in thickness, and lies in its bed, bro- 

 ken as it were by perpendicular fissures into small 

 blocks. It commences with the slate at its sur- 

 face, which surface is nearly horizontal, but takes 



