"Ordinarily, three-dimensionally, yes; but this, no," Seaton assured her. "Remember that our brains and eyes, now really pseudo-fourth-dimensional, are capable of seeing those things as they actually are; but that our entities--intelligences--whatever you like--are still three-dimensional and can neither comprehend nor describe them. We can grasp them only very roughly by transposing them into our own three-dimensional concepts, and that is a poor subterfuge that fails entirely to convey even an approximate idea. As for that horizon--or lack of it--it simply means that this planet is so big that it looks flat. Maybe it _is_ flat in the fourth dimension--I don't know!" Both fell silent, staring at the weird terrain over which they were being borne at such an insane pace. Along its right line above that straight watercourse sped the airship, a shrieking arrow; and to the right of the observers and to left of them spread, as far as the eye could reach, a flatly unbroken expanse of the ghostly, livid, weirdly self-luminous vegetation of the unknowable hyperworld. And, slinking, leaping, or perchance flying between and among the boles and stalks of the rank forest growth could be glimpsed fleeting monstrous forms of animal life. Seaton strained his eyes, trying to see them more clearly; but owing to the speed of the ship, the rapidity of the animals' movements, the unsatisfactory illumination, and the extreme difficulty of translating at all rapidly the incomprehensible four-dimensional forms into their three-dimensional equivalents, he could not even approximate either the size or the appearance of the creatures with which he, unarmed and defenseless, might have to deal. "Can you make any sense out of those animals down there, Peg?" Seaton demanded. "See, there's one just jumped out of the river and seemed to fly into that clump of bamboolike stuff there. Get any details?" "No. What with the poor light and everything being so awful and so distorted, I can hardly see anything at all. Why--what of them?" "This of 'em. We're coming back this way, and we may have to come on foot. I'll try to steal a ship, of course, but the chance that we'll be able to get one--or to run it after we do get it--is mighty slim. But assuming that we are afoot, the more we know about what we're apt to go up against the better we'll be able to meet it. Oh, we're slowing down--been wondering what that thing up ahead of us is. It looks like a cross between the Pyramid of Cheops and the old castle of Bingen on the Rhine, but I guess it's a city--it seems to be where we're headed for." "Does this water actually flow out from the side of that wall, or am I seeing things?" the girl asked. "It seems to--your eyes are all right, I guess. But why shouldn't it? There's a big archway, you notice--maybe they use it for power or something, and this is simply an outfall--" "Oh, we're going in!" Margaret exclaimed, her hand flashing out to Seaton's arm.