was in air or not. This wasn't, at least at the upper extremity....

And then, quite calmly, he turned back to his desk, aimed the antenna straight up, and called Eileen Harmon. She answered promptly.

The stratigrapher listened without interruption to his report and the order to return. She conferred briefly with her companion, replied "We'll be back in twelve hours," and signed off. And that was that.

Zaino settled back with a sign, and wondered whether it would be tactful to remind Rowson of his offer of a year's pay.

All four vehicles were now homeward bound; all one had to worry about was whether any of them would make it. Hargedon and Burkett were fighting their way through an ever-increasing ash rain a scant two miles away—ash which not only cut visibility but threatened to block the way with drifts too deep to negotiate. The wind, now blowing fiercely toward the volcano, blasted the gritty stuff against their front window as though it would erode through; and the lava flow, moving far faster than the gentle ooze they had never quite measured, surged—and glowed—grimly behind.

A hundred miles or more to the east, the tractors containing Mardikian, Marini and their drivers headed southwest along the alternate route their maps had suggested; but Mardikian, some three hours in the lead, reported that he could see four other smoke columns in that general direction.

Mercury seemed to be entering a new phase. The maps might well be out of date.

Harmon and Trackman were having no trouble at the moment, but they would have to pass the great chasm. This had been shooting out daughter cracks when Zaino and Hargedon passed it hours before. No one could say what it might be like now, and no one was going out to make sure.

"We can see you!" Burkett's voice came through suddenly. "Half a mile to go, and we're way ahead of the flow."

"But it's coming?" Rowson asked tensely. He had returned from the power level at Zaino's phoned report of success.

"It's coming."

"How fast? When will it get here? Do you know whether the ship can stand contact with it?"

"I don't know the speed exactly. There may be two hours, maybe five or six. The ship can't take it. Even the temperature measures I got were above the softening point of the 

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