The prince smiled curiously, and his long-fringed lids drooped in momentary contemplation. The auto turned into that majestic avenue which terminates in the Eurychôrus before the Palace of the Litany. St. George's eye eagerly swept the long white way. At its far end stood Mount Khalak. _She_ must have passed over this very ground. "There is," the prince's smooth voice broke in upon his dream, "no such place as Yaque--as you understand 'place.'" "I beg your pardon, your Highness?" St. George doubted blankly. Good Heavens. Maybe there had arrived in Yaque no Olivia, as he understood Olivia. "You showed some surprise, I remember," continued the prince, "when I told you, in McDougle Street, that we of Yaque understand the Fourth Dimension." McDougle Street. The sound smote the ear of St. George much as would the clang of the fire patrol in the midst of light opera. "Yes, yes," he said, his attention now completely chained. Yet even then it was not that he cared so absorbingly about the Fourth Dimension. But what if this were all some trick and if, in this strange land, Olivia had simply been flashed before his eyes by the aid of mirrors? "I find," said the prince with deliberation, "that in America you are familiar with the argument that, if your people understood only length and breadth and did _not_ understand the Third Dimension--thickness--you could not then conceive of lifting, say, a square or a triangle and laying it down upon another square or triangle. In other words, you would not know anything of _up_ and _down_." St. George nodded. This was the familiar talk of college class-rooms. "As it is," pursued the prince, "your people do perfectly understand lifting a square and placing it upon a square, or a triangle upon a triangle. But you do not know anything about placing a cube upon a cube, or a pyramid upon a pyramid _so that both occupy the same space at the same time_. We of Yaque have mastered that principle also," the prince tranquilly concluded, "and all that of which this is the alphabet. That is why 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.