DAVIS: RIVEK TERRACES IN NEW ENGLAND. 



321 



clear how a wandering stream will behave up and down valley from a 

 fixed node. Several suppositions may be made. 



First, the meanders will sweep down the meander belt, and the 

 meander belt will swing to and fro across the valley, but the ampli- 

 tude of both movements will be decreased as the node is approached, 

 and extinguished as it is reached. So far as my observations go, this 

 condition is more appropriate dowu-valley than up-valley from a fixed 

 node. Below the node, slight curves may be formed ; these may develop 

 into normal meanders, Figure 37 (the river flows to the right), as they 

 sweep away from the sill; but such development will probably be grad- 

 ual, and hence the valley floor will widen gradually in that direction. 



""/IliiV"'-- , ■■"Hit , — ■"„„,.' „^ , \ l l'"ll"l»//ll1" 1 ,",4 



Fig. 37. 



Second, the meanders may continue almost in full force as they 

 approach the node from up the valley, merely changing in the lowest 

 part of their course that leads directly to the sill. This might involve 

 the introduction of a " kink " into the meander system, at the point 

 where a change is made from the normal down-sweeping curve to the 

 constrained course that leads to the ledge. That such a sharp bend is 

 possible seems to be shown by certain peculiar forms in the meanders of 

 the Theiss on the plain of Hungary ; it being probable that bends of this 

 kind result from the faster down-sweeping of some meanders than of 

 others. The considerable breadth of flood plain often observed next up- 

 stream from a node supports this supposition. 



Third, the fixed node may perhaps induce the formation of free nodes, 

 evenly spaced from the ledge of superposition ; then between the fixed 

 node and the free nodes, the stream might vibrate as a stretched string 

 vibrates when it is lightly " stopped " at a third or a quarter of its 

 length. Symmetrical free terrace cusps would result from this process. 

 So systematic a movement would seem to be possible only in rare 



