Barnes said:
"Why ... the bottom would wet ... and slide! As if it were greased!"
"Not greased," corrected Hardwick. "Soaped. Soap is viscous. That is different—and a lucky difference! But the least vibration would encourage movement. And it does. It has. So the population is now walking on eggs. Worse, it's walking on the equivalent of a cake of soap which is getting wetter and wetter on the bottom. It's already sliding as a viscous substance does—reluctantly. But in spite of the oil-slick they're trying to keep in place upwind there's still some battering from the sea. There are still some vibrations in the bedrock. And so there's a slow, and gentle, and gradual sliding."
"And they figure," said Barnes abruptly, "that locking onto a ship with the landing-grid might be like an earthquake." He stopped. "An earthquake, now—"
"Not much vulcanism on this planet," Hardwick told him. "But of course there are tectonic quakes occasionally. They made this island."
Barnes said uneasily:
"I don't think, sir, that I'd sleep well if I lived here."
"You are living here for the moment. But at your age I think you'll sleep."
The bolster-truck turned, following the highway. The road was very even, and the motion of the truck along it was infinitely smooth. Its lack of vibration explained why it was permitted to move when all other vehicles were stopped. But Hardwick reflected uneasily that this did not account for the orders of the Sector Chief forbidding the rocket-landing of a ship's boat. It was true enough that the living-surface of the island rested upon slanting stone, and that if the bottom were wet enough it could slide off into the sea. It already had moved. At least one place was moving at four inches per hour. But that was viscous flow. It would be enhanced by vibration, and assuredly the hammering of seas upon the windward cliff should be lessened by any possible means.
But it did not mean that the sound of a rocket-landing would be disastrous, nor that the straining of a landing-grid as it stopped a space-ship in orbit and drew it to ground should produce a landslide. There was something else—though the situation for the island's civilian population was assuredly serious enough. If any really massive movement of the ground did begin, viscous or any other; if any considerable part of the island's surface did begin to move—all of it would go. And the population would go with it. If there were survivors, they could be numbered in dozens.