we are able to keep our island unknown
to the world--not to say 'invisible.'"

For a moment St. George looked at him speechlessly; then, in spite
of himself, a slow smile overspread his face.

"But," he said, "your Highness, there is not a mathematician in the
civilized world who has not considered that problem and cast it
aside, with the word that if fourth-dimensional space does exist it
can not possibly be inhabited."

"Quite so," said the prince, "and yet here we are."

And, if you come to think of it--as St. George did--that is the only
answer to a world of impossibilities already proved possible. But
the vista which all this opened smote him with irresistible humour.

"Ah well now, I suppose, your Highness," he said, "that our ocean
liners sail clean through the island of Yaque, then, and never even
have their smoke pushed sidewise?"

The prince laughed pleasantly.

"Have you ever," he asked, "had occasion to explain the principles
of hydraulics, or chess, or philosophical idealism to a
three-year-old child, or a charwoman? You must forgive me, but
really I can think of no better comparison. I am quite as powerless
now as you have been if you have ever attempted it. I can only
assure you that such things _are_. Without Jarvo or Akko or some one
who understood, you might have sailed the high seas all your life
and never have come any nearer to Yaque."

St. George reflected.

"Is Yaque the only example of this kind of thing," he asked, "that
the Fourth Dimension would reveal?"

"By no means," said the prince in surprise, "the world is
literally teeming with like revelations, once the key is in your
hands. The Fourth Dimension is only the beginning. We utilize that
to isolate our island. But the higher dimensions are gradually
being conquered, too. Nearly all of us can pass into the Fifth at
will, 'disappearing,' as you have the word, from the lower
dimensions. It is well-known to you that in a land whose people
knew length and breadth, but no _up_ and _down_, an object might
be pushed, but never lifted _up_ or put _down_. If it were to be
lifted, such a people would believe it to have 'disappeared.' So,
from you who know only three dimensions, Yaque has 'disappeared,'
until one of us guides you here. Also we pass at will into the
Fifth Dimension and even higher, and seem to 'disappear'; the only
difference is that, there, we should not be able yet to guide one
who did not himself understand how to pas