FISHER: RIVER TERRACES. 
17 
meanders (text-figure C) so long as there is nothing to cause a depar¬ 
ture of the current from the normal. The radius and arc of curvature 
of each meander are definitely controlled by the simple law of deflec¬ 
tion. As the meanders of the river sweep down-stream, they gradually 
deposit on the inner and lower side of each bend a plain sloping gently 
toward the river. Probably no river to-day shows a perfect type series 
of meanders developed by the systematic deflection of the thread of 
fastest current. That the river does not show this systematic arrange¬ 
ment is due to the departure of the current from its delicate adjust- 
Fig. D.—Partition process of lateral movement; early stage. River adjusting 
its meanders to a new deflection of the current. By the growth of one 
sand-bar island, the river parted and has entirely departed from the 
weaker chapnel. Old channel is indicated by the dotted lines. 
ment, incident upon change of volume, cut-off, short-cut, rock barrier, 
accidental natural obstruction, or artificial construction. Any one of 
these controls causes the deflection of the thread of the current, forcing 
the establishment of a new series of curves which cannot coincide with 
the former series. Any change in the direction,of the strongest current 
