The partners, shaking and pale, retreated hastily.  A swift, upward-rising shape swept over the courtyard and was gone—­one of the air-fleet now launched to meet the attackers.

Far below a sudden crumbling shudder of masonry told the Billionaire not a moment was to be lost, for already one wing of the Administration Building was swaying to its fall.

“Quick, Waldron!  Quick!” he shouted, in the shrill treble of senility, and ran into the corridor that led to the north wing.  Waldron, suddenly sobered, followed; and from the offices, where the night-shift of clerks were laboring (or had been, till the first explosion), came crowding pale and frightened men.  Not the fighting cast of Air Trust slaves, these, but the anaemic chemists and experimenters and clerical workers, scabs, to a man.  Now, in the common sentiment of fear, they jostled Flint and Waldron, as though these plutocrats had been but common clay.  And in the corridor a babel rose, through which fresh volleys and ever more and more violent explosions ripped and thundered.

Flint struck savagely at some who barred his way; and Waldron elbowed through, with curses.

“Get out of the way, you swine!” shrilled the old Billionaire.  “Make way, there!  Way!”

The two men reached a door that led by a private passage, through to the steel-and-concrete laboratories.

“Here, this way, Flint!” shouted Waldron.  “If those Hell-devils drop a bomb on us, this building will cave in like jackstraws!  Our only safety is here, here!”

Thoroughly cowed now, with all the brutal bluster and half-drunken swagger gone, Waldron whipped out a bunch of keys, tremblingly unlocked the door and blundered through.  Flint followed.  Behind them, others tried to press, on toward the armored laboratories; but with vile blasphemies the plutocrats beat them back and slammed the door.

“To Hell with them!” shouted Flint, perfectly ashen now and shaking like a leaf, the fear of death strong on his withered soul.  “We’ve got all we can do to look after ourselves!  Quick, Waldron, quick!”

Both men, sick with panic, with fear of the unknown terror from above, stumbled rather than ran along the passage, and presently reached the laboratory.

Here Waldron unlocked another door, this time a steel one, and—­as they both crowded through—­pressed a hand to his dizzy head.

“Safe!” he gulped, slamming the door again.  “They can’t get us here, at any rate, no matter what happens!  This place is like a fort, and—­”

His speech was interrupted by a dazing, deafening tumult of sound.  The earth trembled, and the laboratory, steel though it was, with concrete facing, rocked on its foundation.  A glare through the windows, quickly fading, told them the building they had just quitted was now but a smoking pile of ruin.

Flint gasped, unable to speak.  Waldron, shaking and cowed, tried to moisten his dry lips with a thick tongue.