THE SEINE, THE MEUSE, AND THE MOSELLE 
195 
It is manifest, then, that this valley was excavated by a river 
hardly less vigorous than those that cut the valleys of the Seine 
and the Moselle, but the vigorous river that was once here is 
now nowhere to be found. The floor of the valley is at present 
occupied for the most part by broad, green meadows, instead 
of by a free-swinging current of water, and the only stream to be 
found is the little Meuse, wandering here and there on the broad 
meadows and staggering with most uncertain step around the 
valley curves. It wriggles from place to place, now touching 
this side of the valley, now that, swinging indifferently against 
the steep bluffs and gentle slopes of the spurs, sometimes even 
running for a short distance up the valley in its irregular j)ath. 
Is it not then clear that since the time when this winding valley 
was made there has been a great diminution in the volume of 
water that follows it ? No other conclusion seems admissible; 
and hence a reason for the loss of volume must be sought. (See 
Plates XXIII and XXIV.) 
The loss of volume cannot be ascribed to any climatic change, 
for that should have affected the Seine and Moselle as well. 
May it then be ascribed to a change of the area drained, Avhereby 
the Seine and the Moselle gained the drainage area which the 
Meuse lost? If this were so, the Meuse would have become 
smaller and smaller, while the Seine and Moselle grew larger 
and larger. The dwindling Meuse would have lost the power of 
swinging boldly around its valley curves ; it would have fallen 
into the present timid habit of staggering, after the fashion of 
other small streams, but at the same time the Seine and the 
Moselle would have been confirmed in their vigorous habit of 
swinging freely around the curves of their valle}^s. Is it pos- 
sible, then, that the side branches of the Meuse have really been 
trimmed from the trunk river, and that the trimmed l)ranches 
have been engrafted into the s}^stems of the Seine and the Moselle ? 
The migration of river divides . — The question thus raised leads 
to a consideration of the general problem of the shifting or migra- 
tion of river divides, a subject that is of particular interest to the 
student of ])li3^sical geogra[)hy. At first sight one would be in- 
clined to think that the crest-line of a divide l)etween adjacent 
river basins would merely waste lower and lower as it weathered 
away, without shifting laterally, and therefore without causing 
any change in the area of the adjacent drainage basins. It is 
probable, however, that this sini[)le process is of very rare occur- 
rence in nature. It is much more likely that the line of the 
