Sai 
Notice and Doves of the Reliquic 
ag Diluvianae. 333 
ful agency. We have seen hard, Tiorctien, quartzose 
‘masses, of several tons in weight, torn out of their beds by 
4 mountain torrent, and removed a considerable Spence, 
sete in level countries, and where the stream has no gr 
cept in a few extraordinary instances, even small pebbles, 
dn very many cases of large rivers, it is found, that so far 
from having formed. ae own beds, i are actually i ina 
in the Missour ippi 
as described in Long’s am om I. p.114. The 
uthor believes that the Missouri excavated its own bed, of 
an average depth of one hundred and fifty feet below the 
immediate banks, and three hundred below the great plains 
at a distance on either hand. Yet he says, ‘Sif we admit 
that this great valley with its numerous ramifications, has 
resulted from the operation of currents, wearing down and 
transporting to the ocean the solid materials of ihe earth’s 
surface, it would appear necessary still further to acknowl- 
edge that this channel was once much deeper than at pres- 
ent; for we usually meet with thick alluvial depositions 
_ eovering the rocks that line the bottom of the Missouri vl- 
y. The manifest tendency of the Mississippi, at this time, 
‘upon its valley, is to fill up rather than to excavate; but it 
may be doubted whether this is lest or even to any de- 
gree, the case with the Missouri.” 
Again ; how happens it that the source of a river is fre- 
quently below the head of a valley, if the river excavated 
that valley ? Rivers also sometimes change their beds ; 
_ most sehen wer, sree in our atte 
ag: t the 
could nat notte have bash formed ba sited strea 
But we cannot here enter minutely into this sujet snd 
can only refer our readers to the works of Greenough, 
4 
ee if Boned excavated their own beds, how could they 
p m? And to suppose that rivers formed their 
a ke, i is to suppose they were once without banks. — 
Ree: 
Ascast 
sakes 
