FISHER: RIVER TERRACES. 
21 
change of the current may on the first fill down valley from the neck 
cause a deposition away from the bank and separated from it by a 
narrow strip of water or slough.” Tower also cites a recent cut-off 
at Cole’s Point on the Mississippi where the down-stream fill from 
the cut-off appears “as a distinct island, with a slough behind it, 
indicating a rapid change in the position of the current.” 
A rock barrier likewise deflects the thread of the current causing 
a readjustment of meanders. The sign of the readjustment, viz., 
the partition process, is always more noticeable above and below the 
obstruction and grows less and less prominent up and down stream. 
If a rock barrier is encountered near the apex of a meander, the river 
by withdrawing slightly to the center of its valley may succeed in 
slipping past. The withdrawing and the slipping past indicate a neces¬ 
sary deflection of the thread of the current. Consequently the river 
impinges below the ledge and must withdraw from the channel cut 
above. Sand-bar islands appear when the withdrawal is sudden, 
and the river forms a new series of curves. Should a rock ledge 
be discovered below the apex of a meander, the river is unable to 
slip past, and is strongly compressed above the ledge. Again the 
normal sweep of the meander is prevented, therefore the river above 
and below the compressed curve must conform to the new deflection. 
Sand bars and partition plains are the result. 
Any accidental natural obstruction, which temporarily fills a portion 
of the channel, such as a fallen tree, a slipping down of the sod, a 
piling up of logs, an accumulation of surface debris, etc., effectually 
deflects the current and initiates a new adjustment of meanders. 
The effect of any such artificial obstruction as a pier, dam, or 
bridge is to prevent the river from continuing its normal swinging. 
The river must therefore spend its energy in cutting new meanders 
and filling the deserted portions of its course with deposits and possi¬ 
bly sand bars. The new curves established as the result of a bridge 
differ from curves formed by a cut-off deflection, since a bending must 
occur above and below the bridge, while by cut-off a new meander 
develops, growing outward and down-stream from the cut-off meander. 
A clear example of the partition process exists about seven miles 
from Brattleboro where the Putney road crosses a young meandering 
brook known as Canoe Brook just south of Canoe Brook farm (see 
photographic illustrations, plate 11). The current has withdrawn by 
.successive deflections from a rather well developed series of right- and 
