The moving body had shaken Chet's mental poise as had the earthquake his physical equilibrium. Harkness had not seen it; he was looking off across the level plateau.
"Look!" he exclaimed; "another vent has opened! See it spout?"
Some hundred yards distant were clouds of green vapor that rolled into the air. At their base a fountain of mud sputtered and spouted and fell back to build up a cone. The green cloud whirled sluggishly, then was caught by the breeze and began its slow, rolling progress across the flat rock. It was coming their way, rolling down toward the ship, and Chet gripped suddenly at his companion's arm.
"Come on!" he said! "I'm going away from here, and I'm going now. We'll get Diane and Kreiss: remember what a whiff of gas did to him this morning."
He was drawing Harkness toward the face of the rock; he wondered at his slowness. Walt seemed fascinated by the oncoming cloud.
"Wait!" Harkness paused at the top of the descending slope. Chet turned, to look where Harkness was watching.
The green cloud moved slowly. As he turned to stare it touched the bow of their ship; it flowed slowly, sluggishly, along the sides, and then swept up and over the top. The lookouts of the control room were obscured, and the port from which they had come!
"Cut off!" breathed Harkness, his voice heavy with hopeless conviction. "We can't get back! And now we're on our own past any doubt!"
"It may not last," Chet was urging an hour later, when, with Kreiss and Diane, they stood on high ground to look down on the ship.