MAPS AS GEOGRAPHICAL ILLUSTRATIONS 503 
ing a small economic value to this peculiar stage of river devel- 
opment. 
While the considerable length of the two obsequent streams 
near the elbows of the Soude and Maurienne indicates the lapse 
of a long time since the Surmelin and the Grand Morin were 
beheaded, the absence of any perceptible obsequents at the 
elbows where the forks of the Petit Morin have been captured 
shows that these last changes have been very recently accom- 
plished; the only perceptible alteration since the capture being 
a slight trenching of the rearranged stream-lines below and 
above the elbows. The more active degrading action of the 
diverted streams and the distinct aggrading action of the 
beheaded stream are good examples of correlated development. 
These phases of action are, however, of brief duration. 
Taken all together, this is the simplest, most systematic, 
and most symmetrical example of stream rearrangement that I 
have yet found. It illustrates to perfection the type of rear- 
rangement that is suffered by streams on denuded coastal plains 
where an inner longitudinal lowland is enclosed by an upland 
having a strong inface. This group of sheets is therefore one 
of the most highly prized in our collection. 
THE BAR AND THE AIRE, 
Sheets 24, 35. 
The Bar is a small stream of very irregular course flowing 
through a meadow that follows a meandering valley, whose curves 
have a radius of nearly a mile. The valley bears every mark of 
having been excavated by a stream that had sufficient volume to 
flow smoothly around its curves in the fashion followed by the 
Seine today. The Bar, therefore, appears to be a stream of 
greatly diminished volume. Ascending its valley southward 
from its junction with the Meuse, its meandering curves are 
maintained with almost constant radius, but the volume of the 
stream progressively diminishes, and at Buzancy the marshy 
meadow is left without drainage, except such as has been pro- 
vided by the farmers who have dug ditches between their fields. 
