uld
see at once that Glas Llyn is not an ancient one; and I am not
surprised to find the Government geologists declaring that the Llyn
on Cader Idris is not one either. The fact is, that the crater, or
rather the place where the crater has been, in ancient volcanoes of
this kind, is probably now covered by one of the innumerable bosses
of lava.

For, as an eruption ceases, the melted lava cools in the vents, and
hardens; usually into lava infinitely harder than the ash-cone round
it; and this, when the ash-cone is washed off, remains as the highest
part of the hill, as in the Mont Dore and the Cantal in France, and
in several extinct volcanoes in the Antilles. Of course the lava
must have been poured out, and the ashes blown out from some vents or
other, connected with the nether world of fire; probably from many
successive vents. For in volcanoes, when one vent is choked, another
is wont to open at some fresh point of least resistance among the
overlying rocks. But where are these vents? Buried deep under
successive eruptions, shifted probably from their places by
successive upheavings and dislocations; and if we wanted to find them
we should have to quarry the mountain range all over, a mile deep,
before we hit upon here and there a tap-root of ancient lava,
connecting the upper and the nether worlds. There are such tap-
roots, probably, under each of our British mountain ranges. But
Snowdon, certainly, does not owe its shape to the fact of one of
these old fire vents being under it. It owes its shape simply to the
accident of some of the beds toward the summit being especially hard,
and thus able to stand the wear and tear of sea-wave, ice, and rain.
Its lakes have been formed quite regardless of the lie of the rocks,
though not regardless of their relative hardness. But what forces
scooped them out--whether they were originally holes left in the
ground by earthquakes, and deepened since by rain and rivers, or
whether they were scooped out by ice, or by any other means, is a
question on which the best geologists are yet undecided--decided only
on this--that craters they are not.

As for the enormous changes which have taken place in the outline of
the whole of the mountains, since first their strata were laid down
at the bottom of the sea: I shall give facts enough, before this
paper is done, to enable readers to judge of them for themselves.

The reader will now ask,