VALLEYS. 193 



so on ; and the river issues from the other end clear and 

 refreshed, ready to resume its levelling labours lower 

 down. 



' By such a process of deposition are these wide valleys 

 gradually filled up, and then the river flows gently in a 

 long winding course through the rich territory of its own 

 depositing, like an old man calmly enjoying the fruits of 

 his early toil, and contemplating the good deeds of his 

 youth j for the youthful river, in the brawling early days 

 of its mountain life, is doing good service to the world 

 in thus converting desolation into fertility. Nearly all the 

 fertile plains of the earth have been created thus by the 

 industry of rivers. 



' Besides these there is seen yet another kind of valley, 

 partaking of the characters of both of the above : a long 

 trough-like valley formed by the mountain sides, but which 

 widens as it proceeds downwards, and branches into the 

 great valley of the sea. The waters of the sea fill its lower 

 part, and an estuary, firth, or fiord is formed. These in like 

 manner are continually being filled up by the rivers which 

 come to rest in the waters of the sea, and deposit their 

 burdens there. Thus has Holland, the master-piece and 

 last labour of the Rhine, been formed. 



'The Gula, into whose valley I now descend, presents some 

 illustrations of these river agencies, and a problem to boot. 

 The mounds and knolls that appeared so complex from 

 above are seen from below to be formed by the river cut- 

 ting its way through the alluvium it has deposited, This 

 may have been effected in two ways ; the deposit may have 

 been made in a lake filling a basin-shaped valley, and the 

 river may have cut down and lowered the channel of its 

 outlet considerably beyond its original depth, and thus have 

 not only drained the waters of the lake, but have given suffi- 

 cient inclination and velocity to the river to enable it to 

 carry with it much of the soft earthy matter over which it 

 was flowing ; or it may be that this was an estuary valley, 

 an ancient fiord, up which the sea stretched an arm, the 

 alluvium being deposited by the river when it entered the 



" o 



