264 THE BEAUTIES OF NATURE CHAP, vn 



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, 31, 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. 



