FISHER: RIVER TERRACES. 
27 
from which the parted river departed on its passage to the right across 
the meadow. A natural conclusion would be that the West River, 
having reached the Retreat scarp by the partition process, was with¬ 
drawn by a short-cut to its present position, from which it is again 
moving to the right by the island process. 
At flood season the entire meadow is covered with water. As the 
water subsides, the old channels left by the partition process are occu¬ 
pied by the lingering water, and thus mark with some clearness the 
positions which the stream may have held as it gradually moved to the 
right. Some of the higher levels observed along the banks of the West 
River must have been produced by flooding. The floods are strongly 
marked within this area. Not uncommonly it happens that trees are 
uprooted or lose their bark. The water descends with great sudden¬ 
ness, transporting huge blocks of ice for long distances and often 
twenty feet or more above the present meadow level. As the water 
subsides, such a flood would deposit much material, therefore increas¬ 
ing the height of the river banks, and adding to the sand bars. 
It is quite possible that the swinging of a river from one side of its 
meander belt to the other may be accomplished by a combination of 
short-cut and partition processes. A series of short-cuts produced 
at flood causes the stream at low water to follow in part its old channel 
and in part its new short-cut channel. Such a flood-plain island 
determines the parting of the river and is a measure of its lateral move¬ 
ment. The flood plain exposed on the left-hand side of the West 
River is deeply eroded and cut into at flood season. Should any one 
of these cuts be carved entirely across that flood plain, incision might 
be below the level of the West River channel and so cause a further 
parting of the river around a short-cut island. The largest island in 
the West River, because of its structure, size, and forest vegetation, 
may be a portion of the flood plain separated by a left-hand short-cut. 
The partition plain may be defined as young, mature, or old. The 
young plain is characterized by clearly defined ridges and channels 
of sand-bar material slightly elevated above the water level. So 
recently abandoned are these plains that they show no signs of erosion, 
are rarely grass-covered,— indeed, the probability is that they are still 
swept by floods, receiving additional flood-plain deposits. The mature 
plain is more gently undulating, because the floods have so frequently 
swept over it as to fill in the valleys with fine silt and possibly to remove 
the crests of the ridges. The mature plain is dry, not covered by water, 
