Captain Francis Newcombe's eyes studied the four walls and roof. He spoke more to himself than Runnells.
"Say, six by six by six," he said. "Roughly, two hundred cubic feet. Watertight—hermetically sealed—no air except what's in here now. One hundred cubic feet per man—short work—very short."
"What do you mean?" whispered Runnells with whitening face—and coughed.
"I mean that brute out there, if it still is out there, counts for nothing now," said Captain Francis Newcombe steadily. "We could at least fight that—we can't fight suffocation. I'd say a very few minutes, Runnells, before we're groggy if we can't get air—I don't know how long the rest of it will take."
Runnells screamed. His face grey, beads of sweat suddenly spurting from his forehead, he flung himself against the cement "door," clawing with his finger nails, where no finger nails could grip, around the edges of the block. And then in maniacal frenzy he attacked the wall with his pocketknife.
The blades broke.
Captain Francis Newcombe, with a queer, set smile, drew his revolver, and, holding the muzzle close to the wall, fired. The bullet made little impression. With the muzzle now held over the same spot he fired again.
And now he choked and coughed a little.
The acrid fumes helped to vitiate the air.
"You're making it worse—my Gawd, you're making it worse!" shrieked Runnells. "I can't breathe that stuff into me."