264 THE BEAUTIES OF NATURE cmap. vu 
The width or narrowness of the valley in 
relation to its depth depends greatly on the- 
condition of the rocks, the harder and tougher 
they are the narrower as a rule being the 
valley. 
From time to time:a side stream enters the 
main valley. This is itself composed of many 
smaller rivulets. If the lateral valleys are 
steep, the streams bring with them, especially 
after rains, large quantities of earth and stones. 
When, however, they reach the main valley, 
the rapidity of the current being less, their 
power of transport also diminishes, and they 
spread out the material which they carry down 
in a depressed cone (Figs. 28, 29, 51, 32). 
A side stream with its terminal cone, when 
seen from the opposite side of the valley, pre- 
sents the appearance shown in Figs. 28, 31, 
or, if we are looking down the valley, as in 
Figs. 29, 32, the river being often driven to 
one side of the main valley, as, for instance, 
is the case in the Valais, near Sion, where the 
Rhone (Fig. 30) is driven out of its course by, 
and forms a curve round, the cone brought 
down by the torrent of the Borgne. 
