The Great Dome on Mercury

By Arthur L. Zagat

Darl Thomas mopped the streams of perspiration from his bronzed face and lean-flanked, wiry body, nude save for clinging shorts and fiber sandals. "By the whirling rings of Saturn," he growled as he gazed disconsolately at his paper-strewn desk. "I'd like to have those directors of ITA here on Mercury for just one Earth-month. I'll bet they wouldn't be so particular about their quarterly reports after they'd sweated a half-ton or so of fat off their greasy bellies. 'Fuel consumption per man-hour.': Now what in blazes does that mean? Hey, Jim!" He swiveled his chair around to the serried bank of gauge-dials that was Jim Holcomb's especial charge, then sprang to his feet with a startled, "What's the matter?"

The chunky, red-haired control-man was tugging at a lever, his muscles bulging on arms and back, his face white-drawn and tense. "Look!" he grunted, and jerked a grim jaw at one of the dials. The long needle was moving rapidly to the right. "I can't hold the air pressure!"

"Wow, what a leak!" Darl started forward. "How's it below, in the mine?"

"Normal. It's the Dome air that's going!"

"Shoot on the smoke and I'll spot the hole. Quick, man!"

"Okay!"

Thomas' long legs shot him out of the headquarters tent. Just beyond the entrance flap was one of the two gyrocopters used for flying within the Dome. He leaped into the cockpit and drove home the starter-piston. The flier buzzed straight up, shooting for the misted roof.

The Earthman fought to steady his craft against the hurricane wind, while his gray eyes swept the three-mile circle of the vault's base. He paled as he noted the fierce speed with which the white smoke-jets were being torn from the pipe provided for just such emergencies. His glance followed the terrific rush of the vapor. Big as a man's head, a hole glared high up on the Dome's inner surface. Feathered wisps of tell-tale vapor whisked through it at blurring speed.

"God, but the air's going fast," Darl groaned. The accident he had feared through all the months he had captained Earth's outpost on Mercury had come at last. The Dome's shell was pierced! A half-mile high, a mile across its circling base, the great inverted bowl was all that made it possible for man to defy the white hell of Mercury's surface. Outside was an airless vacuum, a waste quivering under the heat of a sun thrice the size it appears from Earth. The silvered exterior of the hemisphere shot back the terrific blaze; its quartz-covered network of latticed steel inclosed the air that all beings need to sustain life.

Darl tugged desperately at the control-stick, thrust the throttle over full measure. A little more of this swift outrush and the precious air would be gone. He caught a glimpse of the Dome floor beneath him and the shaft-door that gave entrance to the mine below. Down there, in underground tunnels whose steel-armored end-walls continued the Dome's protection below the surface, a horde of friendly Venusians were laboring. If the leak were not stopped in a few minutes that shaft door would blow in, and the mine air would whisk through the hole in its turn. Only the Dome would remain, a vast, rounded sepulcher, hiding beneath its curve the dead bodies of three Earthmen and the silent forms of their Venusian charges.

Darl's great chest labored as he strove to reach the danger spot. Invisible fingers seemed to be clamped about his throat. His eyes blurred. The gyrocopter was sluggish, dipped alarmingly when it should have darted, arrow-like, to its mark. With clenched teeth, the Terrestrian forced the whirling lifting vanes to the limit of their power. They bit into the fast thinning air with a muffled whine, raised the ship by feet that should have been yards.

By sheer will he forced his oxygen-starved faculties to function, and realized that he had reached the wall. He was drifting downward, the hole draining the Dome's air was five feet above him, beyond his reach. The driven vanes were powerless to stem the craft's fall.

One wing-tip scraped interlaced steel, a horizontal girder, part of the vault's mighty skeleton. Darl crawled along the wing, dragging with him a sheet of flexible quartzite. The metal foil sagged under him and slanted downward, trying like some animate thing to rid itself of the unwonted burden. He clutched the beam, hung by one leg and one arm as his craft slid out from beneath him. The void below dragged at him. He put forth a last tremendous spurt of effort.

Two thousand feet below, Jim Holcomb, dizzy and gasping, manipulated the controls frenziedly, his eyes fastened on the dropping pressure-gauge. From somewhere outside the tent a dull thud sounded. "Crashed! Darl's crashed! It's all over!" Hope gone, only the instinct of duty held him to his post. But the gauge needle quivered, ceased its steady fall and began a slow rise. Jim stared uncomprehendingly at the dial, then, as the fact seeped in, staggered to the entrance. "That's better, a lot better," he exclaimed. "But, damn it, what was that crash?"

The headquarters tent was at one edge of the circular plain. Jim's bleary eyes followed the springing arch of a vertical girder, up and up, to where it curved inward to the space ship landing lock that hung suspended from the center of the vaulted roof. Within that bulge, at the very apex, was the little conning-tower, with its peri-telescope, its arsenal of ray-guns and its huge beam-thrower that was the Dome's only means of defense against an attack from space. Jim's gaze flickered down again, wandered across the brown plain, past the long rows of canvas barracks and the derrick-like shaft-head. Hard by the further wall a crumpled white heap lay huddled.

"My God! It was his plane!" The burly Earthman sobbed as his ten-foot leaps carried him toward the wreck.

Darl was his friend as well as Chief, and together they had served the Interplanetary Trading Association, ITA, for years, working and fighting together in the wilds of the outer worlds. A thought struck him, even as he ran. "What in th' name o' Jupiter's nine moons stopped th' leak?" He glanced up, halted, his mouth open in amazement. "Well, I'm a four-tailed, horn-headed Plutonian if there ain't th' boy himself!"

Far up in the interlaced steel of the framework, so high that to his staring comrade he seemed a naked doll, Darl stood outstretched on a level beam, his tiny arms holding a minute square against the wall. Lucky it was that he was so tall and his arms so long. For the saving plate just lapped the upper rim of the hole, and stemmed the fierce current by only a half-inch margin.

The throbbing atmosphere machine in the sub-surface engine-room was replacing the lost air rapidly, and now the increasing pressure was strong enough to hold the translucent sheet against the wall by its own force. Jim saw the extended arms drop away. The manikin waved down to him, then turned to the shell again, as if to examine the emergency repair. For a moment Darl stood thus, then he was running along the girder, was climbing, ape-like, along a latticed beam that curved up and in, to swing down and merge with the bulge of the air-lock's wall.

"Like a bloomin' monkey! Can't he wait till I get him down with th' spare plane?"

But Darl wasn't thinking of coming down. Something he had seen through the translucent repair sheet was sending him to the look-out tower within the air-lock. Hand over hand he swung, tiny above that vast immensity of space. In his forehead a pulse still jumped as his heart hurried new oxygen to thirsty cells. He held his gaze steadily to the roof. A moment's vertigo, a grip