504 SINWOIIE SS IOV SIM QIOY BIN IES, 
Passing still further southward, we come to the Aire, approach- 
ing us in a course that leads directly towards the meandering | 
valley of the Bar, but turning sharply to the west near Grand Pré, 
and in a few miles joining the Aisne, a member of the system 
of the Seine. The present course of the Aire follows a rather 
narrow and steep-sided valley that is trenched beneath remnants 
of a valley plain whose altitude accords closely with the pro- 
longation of the gently ascending meadow-floor of the valley of 
the Bar. All these things considered, there is every reason to 
believe that the Aire once followed the valley of the Bar to the 
Meuse, and that it has been diverted from this path to its present 
course by the headwater growth of a lateral branch of the Aisne. 
The probability of this diversion is further proved in two ways: 
In the first place, the Aire at its junction with the Aisne has a 
height above sea level of 113 meters; the former mouth of 
the Aire in the Meuse had an elevation of 153 meters; the former 
level of the Aire at the point of capture was 182 meters; its 
present floorat this point is 130meters. Evidently, therefore, there 
was good opportunity for the development of a steeper and deeper 
course by the Aire when the chance came for deserting the sys- 
tem of the Meuse and joining that of the Seine. In the second 
place, the Fournelle, a small side-branch of the Aisne, now heads 
close to the Bar, the divide between the two being only six 
meters above the latter, while the mouth of the Fournelle in the 
Aisne is 68 meters lower than the Bar. A little further pushing 
of this divide towards the eastward, and the Bar would be diverted 
precisely as the Aire has already been. 
The meadow that now floors the meandering valley of the 
Bar has every appearance of having been aggraded; this is a 
very natural result of the loss of volume in the beheaded stream, 
which now demands a steeper slope than that which was formerly 
sufficient. 
The head of the Bar is not now immediately adjacent to the 
elbow where the Aire turns westward, but is eleven kilometers 
further north; this distance being occupied by a small stream 
that flows southward to the elbow of capture. The enfeebled 
