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  Transcriber's Note:

  This etext was produced from Astounding Stories April 1932. Extensive research did not uncover any evidence that the U.S. copyright on this publication was renewed.

  "_Once more! Will you give me the recognition signal?"_]

  The Great Dome on Mercury

  By Arthur L. Zagat

  * * * * *

  [Sidenote: Trapped in the great dome, Darl valiantly defends Earth'soutpost against the bird-man of Mars and his horde of pigmy henchmen.]

  Darl Thomas mopped the streams of perspiration from his bronzed faceand lean-flanked, wiry body, nude save for clinging shorts and fibersandals. "By the whirling rings of Saturn," he growled as he gazeddisconsolately at his paper-strewn desk. "I'd like to have thosedirectors of ITA here on Mercury for just one Earth-month. I'll betthey wouldn't be so particular about their quarterly reports afterthey'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 ofgauge-dials that was Jim Holcomb's especial charge, then sprang to hisfeet with a startled, "What's the matter?"

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

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

  "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 beyondthe entrance flap was one of the two gyrocopters used for flyingwithin the Dome. He leaped into the cockpit and drove home thestarter-piston. The flier buzzed straight up, shooting for the mistedroof.

  * * * * *

  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-jetswere being torn from the pipe provided for just such emergencies. Hisglance followed the terrific rush of the vapor. Big as a man's head, ahole glared high up on the Dome's inner surface. Feathered wisps oftell-tale vapor whisked through it at blurring speed.

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

  Darl tugged desperately at the control-stick, thrust the throttle overfull measure. A little more of this swift outrush and the precious airwould be gone. He caught a glimpse of the Dome floor beneath him andthe shaft-door that gave entrance to the mine below. Down there, inunderground tunnels whose steel-armored end-walls continued the Dome'sprotection below the surface, a horde of friendly Venusians werelaboring. If the leak were not stopped in a few minutes that shaftdoor would blow in, and the mine air would whisk through the hole inits turn. Only the Dome would remain, a vast, rounded sepulcher,hiding beneath its curve the dead bodies of three Earthmen and thesilent 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 eyesblurred. The gyrocopter was sluggish, dipped alarmingly when it shouldhave darted, arrow-like, to its mark. With clenched teeth, theTerrestrian forced the whirling lifting vanes to the limit of theirpower. 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, andrealized that he had reached the wall. He was drifting downward, thehole draining the Dome's air was five feet above him, beyond hisreach. The driven vanes were powerless to stem the craft's fall.

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

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

  * * * * *

  The headquarters tent was at one edge of the circular plain. Jim'sbleary eyes followed the springing arch of a vertical girder, up andup, to where it curved inward to the space ship landing lock that hungsuspended from the center of the vaulted roof. Within that bulge, atthe 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'sonly means of defense against an attack from space. Jim's gazeflickered down again, wandered across the brown plain, past the longrows of canvas barracks and the derrick-like shaft-head. Hard by thefurther wall a crumpled white heap lay huddled.

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

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

  Far up in the interlaced steel of the framework, so high that to hisstaring comrade he seemed a naked doll, Darl stood outstretched on alevel 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 savingplate just lapped the upper rim of the hole, and stemmed the fiercecurrent by only a half-inch margin.

  * * * * *

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

  "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 throughthe translucent repair sheet w
as sending him to the look-out towerwithin the air-lock. Hand over hand he swung, tiny above that vastimmensity of space. In his forehead a pulse still jumped as his hearthurried new oxygen to thirsty cells. He held his gaze steadily to theroof. A moment's vertigo, a grip missed by the sixteenth of an inch,the slightest failure in the perfect team-play of eye and brain, andrippling muscle, and he would crash, a half mile beneath, against hardrock.

  At last he reached the curving side of the landing lock. But theplatform at the manhole entrance jutted diagonally below him, fifteenfeet down and twelve along the bellying curve. Darl measured the anglewith a glance as he hung outstretched, then his body became a humanpendulum over the sheer void. Back and forth, back and forth he