16 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Lateral swinging by cut-off process. — The second, or cut-off process 
(Tower, ’04) may be thus briefly stated: when the meanders of a river 
become closely compressed and widely lobate, it is possible for the 
stream to cut off a lobe, desert its old meander course, and follow 
the straighter channel to the sea. Innumerable examples of this 
type have been noted, and may be recognized, if recent, by a lagoon¬ 
shaped lake, silted at the ends, closing toward the river; and later by 
the dry and deserted crescent-shaped channel. 
Lateral swinging by short-cut process. — By the third process, widely 
curving meanders of the river may be deserted during flood season 
through the formation of a new flood-made channel which gives a 
short-cut across the flood plain. Nothing is more evident on the low 
meadows which border our rivers in New England, especially in the 
central and northern portions where the floods are severe, than to find 
channels which have been rudely and cpiickly carved. These channels 
do not cut entirely across the plains, but often extend a few or several 
hundred feet into them. The channel banks are vertical or caving, 
with evidence of small land slides caused by the undercutting of a 
strong, rapid current, which has eaten its way under heavy pressure 
a certain distance, and which in another flood season may extend 
through the flood plain and so serve as a short-cut. Thus the river 
after slowly and elaborately making for itself a wide swinging meander 
wall suddenly desert it for a steeper course to the sea. These processes 
of cut-off and short-cut are very common. 
Lateral swinging by partition process. — There is, perhaps a fourth 
process by means of which a river swings across its belt of wandering. 
This may be called the process of river partition, or the partition 
process. The process is of singular interest. It is by the growth 
of a sand bar within the stream channel that an island is formed and 
the river parted thereby. Eventually the deeper channel acquires 
the entire stream. Thus the deserted channel and the one-time 
island are added to the growing flood plain, and the river has moved 
laterally on its journey across the valley. The formation of other 
islands would again and again part the river, causing it to depart 
successively from the less prosperous channels and so continue to 
move laterally. 
In order better to understand the formation of the sand bar, it is 
well to consider the meandering habit of a river. The current of any 
river tends to sweep down its valley in a series of systematic curves or 
