on showing perfect stratification. There was
no agency in the place to roll these stones, and to deposit these
alternating layers of sand and pebbles, but the river which now rushes
some hundreds of feet below them. At one period of the Via Mala's
history the river must have run at this high level. Other evidences
of water-action soon revealed themselves. From the parapet of the
first bridge I could see the solid rock 200 feet above the bed of the
river scooped and eroded.

It is stated in the guide-books that the river, which usually runs
along the bottom of the gorge, has been known almost to fill it during
violent thunder-storms; and it may be urged that the marks of erosion
which the sides of the chasm exhibit are due to those occasional
floods. In reply to this, it may be stated that even the existence of
such floods is not well authenticated, and that if the supposition
were true, it would be an additional argument in favour of the cutting
power of the river. For if floods operating at rare intervals could
thus erode the rock, the same agency, acting without ceasing upon the
river's bed, must certainly be competent to excavate it.

I proceeded upwards, and from a point near another bridge (which of
them I did not note) had a fine view of a portion of the gorge. The
river here runs at the bottom of a cleft of profound depth, but so
narrow that it might be leaped across. That this cleft must be a
crack is the impression first produced; but a brief inspection
suffices to prove that it has been cut by the river. From top to
bottom we have the unmistakable marks of erosion. This cleft was best
seen on looking downwards from a point near the bridge; but looking
upwards from the bridge itself, the evidence of aqueous erosion was
equally convincing.

The character of the erosion depends upon the rock as well as upon the
river. The action of water upon some rocks is almost purely
mechanical; they are simply ground away or detached in sensible
masses. Water, however, in passing over limestone, charges itself
with carbonate of lime without damage to its transparency; the rock is
dissolved in the water; and the gorges cut by water in such rocks
often resemble those cut in the ice of glaciers by glacier streams. To
the solubility of limestone is probably to be ascribed the fantastic
forms which peaks of this rock usually assume, and also the grottos
and caverns which interpenetrate limestone formations. A rock