"What?"
"Yes, in the beginning there must have been many more than there are now, enough to keep the vast plains looking neat and well-kept, the grass clipped, the forests prevented from encroaching well-defined limits, and so on. But when there were no longer any maintenance men to keep them going, they stopped, one by one, until at this present time there are perhaps a few hundred. Though, I don't know, there may be more. Anyway, whenever one did run down or break down for some reason or other it was soon erased by a still-functioning island."
"Erased?"
"Yes, for it's quite obvious to me that the islands not only cut grass, they kept the plains free of obstructions that weren't supposed to be there. And a dead island would constitute just such a hazard."
Grizquetr spoke in a thin voice, "Perhaps, Father, I may yet understand you. I must be stupid."
"Far from it. You'll learn in time. Anyway, I should have known what they really were when I heard the tales of the sailors. Remember that one about the big hole made by the meteorite? And how something mysterious filled it in and covered it with turf? And then there was the way that wrecked 'rollers would vanish down to the last nut and bolt and the skeletons of the dead aboard. And there was the legend of Samdroo the Tailor Turned Sailor and what he found in the metal chambers inside an island. The great white eye through which he saw what was outside the island. And the other paraphernalia. They weren't the property of a wicked magician, as the tale would have it. Any Earthman would recognize TV and radar and dials and controls."
"Tell me more."
"I will when we get over this wall."
Green had stopped before a barrier of stone, reaching at least forty feet high. A grim crown, it completely encircled the top of the hill. "Once it must have been difficult to scale, but mortar has crumbled here and there, and vines grow all the way up. Follow me. I remember exactly the path I took."
He jumped up on a little ledge, seized a thick vine and hauled himself up to another minor projection. Unhesitatingly, the boy swarmed up after him.