e driven against the track, at the start of an upgrade,
could do it?"

The old peasant woman stood behind the track boss. The thing was a sort
of awful game. She did not speak, but the vicissitudes of the inquiry
advanced her, or retired her, with the effect of points, won or lost.

"I understand perfectly," replied Marion, "how the impact of the heavy
engine might drive both rails out of alignment, if they offered an equal
resistance, or one of them out if it offered a less resistance. This is
straight track. The wedge would go in even. It should have spread
the rails equally. That's the probable thing. But instead it did the
improbable thing; it spread one. I hold the improbable thing always in
question. Human knowledge is built up on that postulate.

"True, a certain factor of difference in conditions must be allowed, as
I have said, but an excessive factor cannot be allowed. We have got
to find it, or discard human reason as an implement for getting at the
truth."

Again the big track boss smashed through the niceties of logic.

"These things happen all the time, Miss Warfield. You can't figure it
out."

"One ought to be able to determine it,"' replied the girl.

The track boss shook his head.

"We can't tell what made that rail give."

"Of course, we can tell," said Marion. "It gave because it was
weakened."

"But what weakened it?" replied the man. "You can't tell that? The
rail's sound."

"There could be only two causes," said Marion. "It was either weakened
by a natural agency or a human agency."

The track boss made an annoyed gesture, like a practical person vexed
with the refinements of a theorist.

"But how are you going to tell?"

"Now," said Marion, "there is always a point as you follow a thing down,
where the human design in it must appear, if there is a human design in
it. The human mind can falsify events within a limited area. But if one
keeps moving out, as from a center, he will find somewhere this point at
which intelligence is no longer able to imitate the aspect of the result
of natural forces... I think we have reached it."

She paused and drove her query at the track boss.

"The spikes on the outside of this rail held it in place, did they not?"

"Yes, Miss Warfield."

"Did the impact of the engine force these spikes out of the ties?"

"Yes, Miss Warfield, it forced them out."

"How do you know it forced them out?"

"Well, Miss Warfield," said the man, pointing to the