ps were not, I think, originally isolated, but connected
with the adjoining ranges. If we assume that Plato was once an enclosed
sea, or lake, which burst through the mountain walls--possibly owing to
their being weakened or broken by volcanic action--there would have been
a tremendous outrush of water, which must have carried away a good deal
of the softer material of these hills and mountains; whilst, in after
years, the continual wash of the waters, combined with aerial
denudation, would gradually have worn away all but the hardest parts of
these formations.

"Most probably the whole of the surrounding area was also at some time a
sea, though volcanic action has since altered its surface conformation,
and in places it bears evidence of having been covered with lava. It is
not unusual on our world for volcanoes to burst up from under the sea,
so even the evidence of volcanic action does not, as some seem to think,
negative the possibility of water ever existing here; and it may not be
inappropriate to point out that our hydrographers have proved that our
ocean-beds are not always smooth, but are often diversified by high
hills and deep valleys."

M'Allister here interjected: "Professor, would you kindly tell us
something about that fine range of mountains over yonder, just to the
right hand?"

"Oh yes," I replied; "I was just about to mention that mountain range,
which is called the Alps after those in Switzerland; and that peak on
the front portion, just south of the great valley you see, is named Mont
Blanc, and is about 12,000 feet in height.

"You will notice a very large number of peaks in this and the other
neighbouring ranges--in fact, several thousands have been marked on our
large maps.

"Cutting diagonally in a north-westerly direction, completely through
the Alps, you will notice a long and deep valley. This is known as the
'Great Alpine Valley,' and is over eighty miles long, and varies from
about three miles to six and a half miles in width. At the eastern end
it is some 11,000 feet deep, debouching on to the plain in several
comparatively narrow passes, whilst at its north-western extremity it is
very shallow, and emerges on to what is known as the Sea of Cold, which
covers an area of about 100,000 square miles. This valley seems to
afford another example of formation by the action of water.

"Amongst the three thousand peaks comprised in the Apennine range just
below the Alps, are several mountai