326 THE BEAUTIES OF NATURE CHAr. 



of its course, nor deposits materials, it is said 

 to have acquired its " regimen," and in such 

 a case if the character of the soil remains the' 

 same, the velocity must also be uniform. The 

 enlargement of the bed of a river is not, how- 

 ever, in proportion to the increase of its wa- 

 ters as it approaches the sea. If, therefore, 

 the slope did not diminish, the regimen would 

 be destroyed, and the river would again com- 

 mence to eat out its bed. Hence as rivers 

 enlarge, the slope diminishes, and consequently 

 every river tends to assume some such "regi- 

 men" as that shown in Fig. 46. 



Now, suppose that the fall of the river is 

 again increased, either by a fresh elevation, 

 or locally by the removal of a barrier. Then 

 once, more the river regains its energy. Again 

 it cuts into its old bed, deepening the valley, 

 and leaving the old plain as a terrace high 

 above its new course. In many valleys sev- 

 eral such terraces may be seen, one above 

 the other. In the case of a river running in a 

 transverse valley, that is to say of a valley 

 lying at right angles to the "strike" or direc- 

 tion of the strata (such, for instance, as the 



