. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. DAVIS: RIVER TERRACES IN NEW ENGLAND. 321 clear how a wandering stream will behave up and down valley from a fixed node. Several suppositious 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 down-valley than up-valley from a fixed node. Below the node
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. DAVIS: RIVER TERRACES IN NEW ENGLAND. 321 clear how a wandering stream will behave up and down valley from a fixed node. Several suppositious 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 down-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. ^^^i^piiili^^'^. m:ii^''!im M\€^M'/m\iu $mi''^-''^?^s&sii 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 thii-d or a quarter of its length. Symmetrical
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