reassumes its importance. There is a very interesting example of this
in the history of France. Before Roman civilisation reached the north
of Gaul the Seine and its tributary streams were evidently the chief
economic factor in the life of the people: this may be seen in the
sites of their strongholds and in the relation of the tribes to one
another, as for instance, the dependence of the Parisians upon Sens.
The five centuries of active Roman civilisation saw the river replaced
by the system of Roman roads; the great artificial track from north to
south, for instance, takes on a peculiar importance; but when the end
of that period has come, and the energies of the Roman state are
beginning to drag, when the money cannot be collected to repair the
great highways, and these fall into decay--then the Seine and its
tributaries reassume their old importance. Paris, the junction of the
various waterways, becomes the capital of a new state, and the
influence of its kings leads out upon every side along the river
valleys which fall into the main valley of the Seine.

There are but two considerable modifications to the use for habitation
of slow and constant rivers: their value is lessened or interrupted by
precipitous banks or they are rendered unapproachable by marshes. The
first of these causes, for instance, has singularly cut off one from
the other the groups of population residing upon the upper and the
lower Meuse, as it has also, to quote another example, cut off even in
language the upper from the lower Elbe.

From this first species of interruption the Thames is, of course,
singularly free. There is no river in England, with the exception of
the Trent, whose banks interfere so little with the settlement of men
in any place on account of their steepness.