A moment and the cloud began to fill the air about us. There was a
paralyzing odor. I looked about at the others, gasping and
coughing. As the cloud rolled on, inexorably increasing in
density, it seemed literally to grip the lungs.

It flashed over me that already the engineer and fireman had been
overcome, though not before the engineer had been able to stop the
train.

As the cloud advanced, the armed guards ran from it, shouting, one
now and then falling, overcome. For the moment none of us knew
what to do. Should we run and desert the train for which we had
dared so much? To stay was death.

Quickly Kennedy pulled from his pocket the gauze arrangements he
had had in his hand that morning just as Miss Euston's knock had
interrupted his conversation with me. Hurriedly he shoved one into
Miss Euston's hands, then to Lane, then to me, and to the guard
who was with us.

"Wet them!" he cried, as he fitted his own over his nose and
staggered to a water-cooler.

"What is it?" I gasped, hoarsely, as we all imitated his every
action.

"Chlorin gas," he rasped back, "the same gas that overcame
Granville Barnes. These masks are impregnated with a glycerin
solution of sodium phosphate. It was chlorin that destroyed the