24 ACCOUNT or tue SPRAY 
broke down the rock for the fpace of thefe fix or feven 
miles. Some have fuppofed that from thefe appearances, 
conjectures might be formed of the age of this part of the 
world.—To enter upon fuch a calculatioa, it would pre- 
vioully be neceflary to afcertain how much the fall had re- 
tired in a hundred years, or any other certain period— 
Suppofe that we were even in pofleffion of fucha fad, ftill 
the conclufions drawn from it would be liable to the 
greate{t uncertainty, as it is evident that the {pace of rock 
broke down and worn away in a certain number of years 
would not always be the fame.—The more or lets hard- 
nefs and brittlenefs of the rock in different parts; the 
greater or lefs feverity of the frofts in different years; and 
the quantities of water that flowed at different periods in 
the cataract of the river, would all occafion confiderable 
variations. This retroceflion of the Falls does not by any 
means go on fo quickly as fome have imagined. During 
nine years that I have remained at Niagara, very few 
pieces of the rock have fallen down which were large e- 
nough tomake any fenfible alteration in the brink; and in 
the {pace of two years I could not perceive, by a pretty ac- 
curate meafurement, that the North-Eaft brink had in the 
leaft receded. If we adopt the opinion of the Falls having 
retired fix miles, and if we fuppofe the world to be 5700 
years old, this will give above fixty-fix inches and an half 
fora year, or fixteen yards and two thirds for nine years, 
which I can venture to fay has not been the cafe fince 1774. 
But if weaccede to the opinion of fome modern philofophers, 
and fuppofe that America has emerged much laterthan the 
other parts of the world, it will neceffarily follow that 
this retrograde motion of the Falls muft have been quicker, 
which is a fuppofition ftill lefs confonant to the obfervati- 
ons of late years. 
Obfervations 
