302 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
the stage of development may be stated in terms of the flood-plain 
pattern. 
The four postulates above announced concerning river action may 
therefore be taken as well supported. 
A natural limit is set to the dimensions of a growing meander curve 
on a flood plain by the formation of short-cuts across flood-plain lobes at 
time of high water, or of cut-offs when the narrowing neck of a lobe is 
finally worn through, a roundabout course being in both cases abandoned 
for a more direct one. It may therefore be expected that the abandoned 
channels, such as are preserved in ox-bow lakes on existing flood plains, 
and in swampy half-filled channels at the back border of many terraces, 
will on the average show a larger radius of curvature than the curves 
of the existing river ; and the maps of the Mississippi give some support 
to this expectation. Emerson has pointed out (735) the tendency of our 
New England rivers and streams to form loops or ox-bows on the right 
of their general course, from which they return to a nearly direct course 
by short-cuts or cuts-offs, only to begin again the work of right-handed 
loop-cutting. He states that the Connecticut near Northampton, Mass., 
has seven deserted loops on the right (west) and none on the left; some 
of its tributaries have sharp bends and ox-bows thirty times as numerous 
on the right as on the left of their course. It is naturally suggested 
that this asymmetry is the result of the deflective force arising from the 
earth’s rotation. 
TERMINOLOGY OF WANDERING Rivers. The terms already introduced 
regarding rivers that wander about their flood plains may now be sum- 
marized and somewhat extended. The space enclosed between tangents 
drawn outside of the curves or meanders of the stream is the 
meander belt. This belt will widen while the meanders are normally 
wearing their outer bank ; but on the occurrence of a short-cut across a 
flood-plain lobe or of a cut-off through the narrowing neck of a lobe, the 
belt will locally collapse. Here the river course becomes relatively 
direct for a time, only to develop serpentines again as new meanders are 
established. The progressive movement of the meanders down the 
valley will be called sweeping. Up-stream and down-stream will be 
used in their ordinary sense, but up-valley and down-valley will be 
substituted when it is desired to indicate a more general direction than 
that of the circuitous channel. 
The lateral movement of the meander belt from one side of the valley 
floor to the other will be referred to as swinging. It is not always 
possible to distinguish between the true lateral swinging of the meander 
