really sailed to the west or to the south.

As, for the most part, those who were left behind were ignorant, rude,
and unlettered, it consequently happened that many of the marvellous
things which the ancients did, and the secrets of their science, are
known to us by name only, and, indeed, hardly by name. It has happened
to us in our turn as it happened to the ancients. For they were aware
that in times before their own the art of making glass malleable had
been discovered, so that it could be beaten into shape like copper. But
the manner in which it was accomplished was entirely unknown to them;
the fact was on record, but the cause lost. So now we know that those
who to us are the ancients had a way of making diamonds and precious
stones out of black and lustreless charcoal, a fact which approaches the
incredible. Still, we do not doubt it, though we cannot imagine by what
means it was carried out.

They also sent intelligence to the utmost parts of the earth along wires
which were not tubular, but solid, and therefore could not transmit
sound, and yet the person who received the message could hear and
recognise the voice of the sender a thousand miles away. With certain
machines worked by fire, they traversed the land swift as the swallow
glides through the sky, but of these things not a relic remains to us.
What metal-work or wheels or bars of iron were left, and might have
given us a clue, were all broken up and melted down for use in other
ways when metal became scarce.

Mounds of earth are said to still exist in the woods, which originally
formed the roads for these machines, but they are now so low, and so
covered with thickets, that nothing can be learnt from them; and,
indeed, though I have heard of their existence, I have never seen one.