IV

For a moment, he thought that the _Albireo_ had been flung bodily into

the air. Then he decided that the great metal pillar had merely fallen

over. Finally he realized that the ship was still erect, but the ground

under it had just tried to leave.

Everyone in the group had become so used to the almost perpetual ground

tremors that they had ceased to notice them; but this one demanded

attention. Rowson, using language which suggested that his career

might not have been completely free of adventure after all, flashed

through the communication level on his way down to the power section.

Schlossberg and Babineau followed, the medic pausing to ask Zaino if he

were all right. The radioman merely nodded affirmatively; his attention

was already back at his job. Burkett was speaking a good deal faster

than before.

"Never mind if the sample isn't lashed tight yet--if it falls off

there'll be plenty more. There isn't time! Arnie, get in touch with Dr.

Mardikian and Dr. Marini. Tell them that this volcano is explosive,

that all estimates of what the flow may do are off until we can make

more measures, and in any case the whole situation is unpredictable.

Everyone should get back as soon as possible. Remember, we decided that

those big craters Eileen checked were not meteor pits. I don't know

whether this thing will let go in the next hour, the next year, or at

all. Maybe what's happening now will act as a safety valve--but let's

get out. Ren, that flow is speeding up and getting higher, and the ash

rain is getting a lot worse. Can you see to drive?"

She fell silent. Zaino, in spite of her orders, left his set long

enough to leap to the nearest port for a look at the volcano.

He never regretted it.

Across the riven plain, whose cracks were now nearly hidden under the

new ash, the black cone towered above the nearer elevations. It was

visibly taller than it had been only a few hours before. The fountain

from its top was thicker, now jetting straight up as though wind no

longer meant a thing to the fiercely driven column of gas and dust. The

darkness was not so complete; patches of red and yellow incandescence

showed briefly in the pillar, and glowing sparks rather than black

cinders rained back on the steep slopes. Far above, a ring of smoke

rolled and spread about the column, forming an ever-broadening blanket

of opaque cloud above a landscape which had never before been shaded

from the sun. Streamers of lightning leaped between cloud and pillar,

pillar and mountain, even cloud and ground. Any thunder there might

have been was drowned in the howl of the escaping gas, a roar which

seemed to combine every possible note from the shrillest possible

whistle to a bass felt by the chest rather than heard by the ears.

Rowson's language had become inaudible almost before he had disappeared

down the hatch.

For long moments the radioman watched the spreading cloud, and wondered

whether the _Albireo_ could escape being struck by the flickering,

ceaseless lightning. Far above the widening ring of cloud the smoke

fountain drove, spreading slowly in the thinning atmosphere and beyond

it. Zaino had had enough space experience to tell at a glance whether

a smoke or dust cloud 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 alloys, and it's hotter and much

deeper now. Anyway, if the others aren't back before the flow reaches

the ship they won't get through. The tractor wheels would char away,

and I doubt that the bodies would float. You certainly can't wade

through the stuff in a spacesuit, either."

"And you think there can't be more than five or six hours before the

flow arrives?"

"I'd say that was a very optimistic guess. I'll stop and get a better

speed estimate if you want, but won't swear to it."

Rowson thought for a moment.

"No," he said finally, "don't bother. Get back here as soon as you can.

We need the tractor and human muscles more than we need even expert

guesses." He turned to the operator.

"Zaino, tell all the tractors there'll be no answer from the ship for a

while, because no one will be aboard. Then suit up and come outside."

He was gone.

* * * * *

Ten minutes later, six human beings and a tractor were assembled in the

flame-lit near-darkness outside the ship. The cloud had spread to the

horizon, and the sun was gone. Burkett and Hargedon had arrived, but

Rowson wasted no time on congratulations.

"We have work to do. It will be easy enough to keep the lava from the

ship, since there seems to be a foot or more of ash on the ground and

a touch of main drive would push it into a ringwall around us; but

that's not the main problem. We have to keep it from reaching the

chasm anywhere south of us, since that's the way the others will

be coming. If they're cut off, they're dead. It will be brute work.

We'll use the tractor any way we can think of. Unfortunately it has no

plow attachment, and I can't think of anything aboard which could be

turned into one. You have shovels, such as they are. The ash is light,

especially here, but there's a mile and a half of dam to be built. I

don't see how it can possibly be done ... but it's going to be."

"Come on, Arnie! You're young and strong," came the voice of the

mineralogist. "You should be able to lift as much of this stuff as I

can. I understand you were lucky enough to get hold of Eileen--have you

asked for the bonus yet?--but your work isn't done."

"It wasn't luck," Zaino retorted. Burkett, in spite of her voice,

seemed much less of a schoolmistress when encased in a spacesuit and

carrying a shovel, so he was able to talk back to her. "I was simply

alert enough to make use of existing conditions, which I had to observe

for myself in spite of all the scientists around. I'm charging the

achievement to my regular salary. I saw--"