ound Vesuvius, and in so many West Indian
Islands; the last confusion of which is very likely to be this:

That when the volcano has succeeded--as it did in the case of Sabrina
Island off the Azores in 1811, and as it did, perhaps often, in
Snowdonia--in piling up an ash cone some hundred feet out of the sea;
that--as has happened to Sabrina Island--the cone is sunk again by
earthquakes, and gnawn down at the same time by the sea-waves, till
nothing is left but a shoal under water. But where have all its vast
heaps of ashes gone? To be spread about over the bottom of the sea,
to mingle with the mud already there, and so make beds of which, like
many in Snowdon, we cannot say whether they are of volcanic or of
marine origin, because they are of both.

But what has all this to do with the slates?

I shall not be surprised if my readers ask that question two or three
times during this paper. But they must be kind enough to let me tell
my story my own way. The slates were not made in a day, and I fear
they cannot be explained in an hour: unless we begin carefully at
the beginning in order to end at the end. Let me first make my
readers clearly understand that all our slate-bearing mountains, and
most also of the non-slate-bearing ones likewise, are formed after
the fashion which I have described, namely, beneath the sea. I do
not say that there may not have been, again, and again, ash-cones
rising above the surface of the waves. But if so, they were washed
away, again and again, ages before the land assumed anything of its
present shape; ages before the beds were twisted and upheaved as they
are now.

And therefore I beg my readers to put out of their minds once and for
all the fancy that in any known part of these islands craters are to
be still seen, such as exist in Etna, or Vesuvius, or other volcanoes
now at work in the open air.

It is necessary to insist on this, because many people hearing that
certain mountains are volcanic, conclude--and very naturally and
harmlessly--that the circular lakes about their tops are true
craters. I have been told, for instance, that that wonderful little
blue Glas Llyn, under the highest cliff of Snowdon, is the old crater
of the mountain; and I have heard people insist that a similar lake,
of almost equal grandeur, in the south side of Cader Idris, is a
crater likewise.

But the fact is not so. Any one acquainted with recent craters wo