Flint, for the first time hearing Waldron’s honest opinion of him, failed even to note it.  All his panic-stricken ear had caught was the note of hope, of survival.

Clutching eagerly at Waldron’s sleeve, he cackled: 

“If we get through?  If we get through, you say?  Then, in your opinion, there is a chance to get through?  They can’t get us here?  We surely shall be rescued?”

“Bah!” Waldron flung at him, some latent spark of courage still smouldering in his sodden breast, whereas old Flint was craven to the marrow.  “You nauseate me!  Afraid to die, eh?  Well, so am I; but not so damned paralyzed and sick with panic as all that!  If you’d taken less dope, the last twenty years, you’d have more nerve now, to face the music!  World-master, you?  Eh?  Playing the biggest game on earth—­and now, when things break bad, you squeal!  Arrrh!  You called me a quitter once, you mealy-mouthed old Pecksniff!  We’ll see, now, who quits!  We’ll see, at a show-down, who can face it, you or I!”

[Illustration:  His fingers lost their hold—­he dropped like a Plummet.]

Waldron’s brutality, the hard, savage quality that all his life had made him “Tiger” Waldron, now was beginning to reassert itself.  His first sheer panic over, a little manhood was returning.  But as for Flint, no manhood dwelt in him to be awakened.  Instead, each moment found him more abject and more pitiable.  Like an old woman he now wrung his hands and groaned, hysterically; and now he paced the steel floor of the vault that was destined to be his tomb; and now he stopped again and stared about him with wild eyes.

On all sides, sheer up a hundred feet or more, the smooth steel sides of the vast oxygen tank rose, studded with long lines of rivets.

Near the top a dark aperture showed where the six-inch pipe joined the tank; the pipe destined to fill it, when Herzog’s last process—­never, now, to be completed—­should have been done.

The huge floor, 150 feet in diameter, sloped gently downward toward the center; and here yawned another pipe, covered by a grating—­the pipe to drain the liquid oxygen out to the pumping station.

So deeply set in the rock of the Niagara cliff was this stupendous tank, and so cunningly surrounded by vacuum-chambers, that now no faintest sound of the Falls was audible.  All that betrayed the nearness of the cataract was a faint, incessant trembling of the metal walls, as though the solid ribs of Earth herself were shuddering with the impact of the plunge.

Old Flint surveyed this extraordinary chamber with mingled feelings.  It surely offered absolute protection, for the present—­or seemed to—­but his distressed mind conjured alarming pictures of the future, in case no rescue came.  Death by starvation, thirst and madness loomed before him.  Nervously he recommenced his pacing.  Another terribly serious factor was to be considered.  He had now been three hours without his dose of morphia, and his nerves were calling, tugging insistently for it.