It's a train."

We heard the roar of it, and presently it came flying into sight, going
at what seemed to me to be a prodigious speed. Whence it had come, or
how far, we had no means of knowing. Only by some miracle of luck could
it have gone any distance. But now we were to see the terrific end of
its career. A train of coal trucks stood motionless upon the line. We
held our breath as the express roared along the same track. The crash
was horrible. Engine and carriages piled themselves into a hill of
splintered wood and twisted iron. Red spurts of flame flickered up from
the wreckage until it was all ablaze. For half an hour we sat with
hardly a word, stunned by the stupendous sight.

"Poor, poor people!" cried Mrs. Challenger at last, clinging with a
whimper to her husband's arm.

"My dear, the passengers on that train were no more animate than the
coals into which they crashed or the carbon which they have now become,"
said Challenger, stroking her hand soothingly. "It was a train of the
living when it left Victoria, but it was driven and freighted by the dead
long before it reached its fate."

"All over the world the same thing must be going on," said I as a vision
of strange happenings rose before me. "Think of the ships at sea--how
they will steam on and on, until the furnaces die down or until they run
full tilt upon some beach. The sailing ships too--how they will back and
fill with their cargoes of dead sailors, while their timbers rot and
their joints leak, till one by one they sink below the surface. Perhaps
a century hence the Atlantic may still be dotted with the old drifting
derelicts."

"And the folk in the coal-mines," said Summerlee with a dismal chuckle.
"If ever geologists should by any chance live upon earth again they will
have some strange theories of the existence of man in carboniferous
strata."

"I don't profess to know about such things," remarked Lord John, "but it
seems to me the earth will be 'To let, empty,' after this. When once our
human crowd is wiped off it, how will it ever get on again?"

"The world was empty before," Challenger answered gravely. "Under laws
which in their inception are beyond and above us, it became peopled. Why
may the same process not happen again?"

"My dear Challenger, you can't mean that?"

"I am not in the habit, Professor Summerlee, of saying things which I do
not mean. The observation is trivial." Out went the beard and down came