alleys, is that of habitable and fertile countries formed by the
attrition of those rivers; and to perceive the operation of water
wearing down the softer and less solid parts, while the more hard and
solid rocks of the ridges, as well as scattered mountains, had resisted
and preserved a higher station.

In this map, for example, let us suppose the first and second ridge of
our author's plan to be joined at the mouth of the Loire, and retain the
water of that river, as high as the summit of its surrounding ridges;
this great valley of the Loire, which at present is so fine and fertile
a country, would become a lake; in like manner as the proper valley of
the Rhone, above St Maurice, would be drowned by shutting up that gap of
the mountains through which the Rhone passes in order to enter the plain
of Geneva.

This is the view that P. Chrysologue takes of those small valleys formed
between the ridges of the Jura. But this is not perhaps the just view of
the subject; for though by closing the gap by which the Loire or Rhone,
passes through the inclosing ridge, the present country above would
certainly be overflowed by the accumulated waters, yet it is more
natural to suppose, that the great gap of the Loire, or the Rhone, had
been formed gradually, in proportion as the inclosed country had been
worn down and transported to the sea. We have but to consider, that the
attrition of those transported materials must have been as necessary for
the hollowing out of those gaps in the solid rock of the obstructing
mountains, as the opening of those gaps may have been for the
transporting of those materials to the sea. But it is perhaps
impossible, from the present appearance of things, to see what
revolutions may have happened to this country in the course of its
degradation; what lakes may have been formed; what mountains of softer
materials may have been levelled; and what basons of water filled up and
obliterated.

This general view of the valley of the Loire, and all its branches, is
perhaps too extensive to be admitted in this reasoning from effect to
cause; we must approximate it by an intermediate step, which will easily
be acknowledged as entering within the rule. It is in Forrez, near the
head of the Loire. There we find the plain of Mont Brison, 40,000 toises
or 22 miles long and half as wide, surrounded by a ridge of granite
mountains on every side. Here the river, which is a small branch of
the Loire, enters at the u