l)ary ®‘*'^nges produced bv river*. 315 
liave been rendered arid deserts by Ibis inad- 
osii,„'„ clouds from tlie Western Ocean would 
passed over England witliout disturbance 
■.js, jj'^°’’‘ 5 ucting powers of leaves of trees, or blades 
^I's ■ .. coal- works had not saved our natural con- 
this Thames, the agent of so much abun- 
rnuch wealtli, might, in that case, have be- 
icnj, like tire once equally famed Jordan, 
I or 
iij, ajj ^®®t^ended towards a rude space near the Thames, 
it, *^o\K,ij‘*®®t'ed to be in toe state in which the occasional 
iiiji ^tid gradual retrocession of the river had left 
liatj those wastes which the lord of the 
Uot yet enabled some industrious cultivator to 
in 
large tracts of which Great Britain still 
it ^tirface of the earth in the pristine state in 
"pj. * left bv the spcnridarv causes that have viven it 
Mie T secondary causes that have given it 
Hj^tire ..j ^®mes, doubtless, in a remote age, covered 
'C|*'^^lve5 i > but it is the tendency of rivers to nan’ow 
, ; : . 
!,'^jl''t)us degrees of fall produce every variety of 
every variety of banks, in 
ch iu due time, the course of the river 
i'Vx*'!!* where a flat succeeds a rapid, and the 
’ promoting prolific vegetable creations on 
'trr?'‘ die '^,'^p^dy increasing and encroaching banks, 
lil-.,- .b^ts then form lakes 
‘ .generate encroachi 
'■-,11)5^ when new rivei 
H ^beir (urn, become interrupted, and re- 
Sr K encroaching banks, which fini 
fivers are formed on big 
the interior. These 
which finally 
her 
causes produce one class 
s' ^bons of land above the level of the sea, 
^ tttueh puzzled geologists. The only con- 
itself '• ^’■^fbice of dry land requires to increase 
an 
IS the absence of salt-water, consequent on 
nccumulatiou of vegetable and animal 
t'ff has not latterly been allowed to produce its 
Xlt.tects K - 
2? inV , . for two thousand years the banks 
Nllf''‘’'al 1;^ by man, who, unable to appreciate 
by which the phenomena of the earth are 
^dulously kept open the course of the river, 
'trmation of interior lakes. The Cm- 
