or THE FALLS or NIAGARA, &c. 21 
bove the Falls, perhaps never ata much greater diftance 
than one mile below them. Clofe to the Falls it is found 
between the layers of moft of the rocks, the quantity lef- 
{ening in proportion to thediftance from the Falls. Upon 
comparing all thefe circumftances together, it feems pro- 
bable that this fubftance is formed by the moifture arifing 
from the Falls conftantly and flowly filtering between the 
layers of the rocks; and it feems very poffible that the vio- 
jent agitation which the water has undergone may difpofe 
it to part with its earth more eafily than it otherwife would 
do.—The circumftance of this{pray not being found above 
the Falls feems to fuggeftan opinion that that part of the 
vapour which hangs upon the furrounding rocks is the 
heavieltas being moft loaded with earthy particles, whilft the 
remainder which mounts up is the pureft and contains lit= 
tle ornoearth. The want of proper rocks to filter through 
and to attract the earthy particles may likewife be a reafon 
why the {pray is not found above the Falls, and the {peci- 
fic gravity of the water which runs down the channel of 
the river below the Falls being equal to that of the water 
above them (which feems to argue that from want of fome 
attracting body it had parted with little or none of its earth) 
favours fuch a fuppofition. 
The reafon why fo little progrefs has hitherto been made 
in inveftigating the natural formation of this concrete 
feems to be, that travellers who have only an opportunity 
of feeing the Falls once or twice, have fo many more in- 
terefting objecis within their view, that they have little 
Jeifure, and lefs inclination, to fearch for it amongit the 
rocks; and generally content themfelves with the pieces 
which they find amongft the ftones on the beach. To thofe 
who find itin this fituation, and who do not attempt to dif- 
cover how it came there, its formation muft appear utterly 
incomprehenfible. To explain this matter clearly we have 
only to recolle&t what has been faid of the frequent fall of 
parts 
