the base of the cliff we heard some very strange noises from above."

"But the creature that the American drew? How do you account
for that?"

"We can only suppose that he must have made his way to the summit
and seen it there. We know, therefore, that there is a way up.
We know equally that it must be a very difficult one, otherwise the
creatures would have come down and overrun the surrounding country.
Surely that is clear?"

"But how did they come to be there?"

"I do not think that the problem is a very obscure one," said the
Professor; "there can only be one explanation. South America is,
as you may have heard, a granite continent. At this single point
in the interior there has been, in some far distant age, a great,
sudden volcanic upheaval. These cliffs, I may remark, are
basaltic, and therefore plutonic. An area, as large perhaps as
Sussex, has been lifted up en bloc with all its living contents,
and cut off by perpendicular precipices of a hardness which
defies erosion from all the rest of the continent. What is
the result? Why, the ordinary laws of Nature are suspended.
The various checks which influence the struggle for existence in
the world at large are all neutralized or altered. Creatures survive
which would otherwise disappear. You will observe that both the
pterodactyl and the stegosaurus are Jurassic, and therefore of a
great age in the order of life. They have been artificially
conserved by those strange accidental conditions."