Alexander grew impatient. "That's all true, Phil, but we never were
justified in assuming that a scale that was perfectly safe for an
ordinary bridge would work with anything of such length. It's all very
well on paper, but it remains to be seen whether it can be done in
practice. I should have thrown up the job when they crowded me. It's
all nonsense to try to do what other engineers are doing when you know
they're not sound."
"But just now, when there is such competition," the younger man
demurred. "And certainly that's the new line of development."
Alexander shrugged his shoulders and made no reply.
When they reached the bridge works, Alexander began his examination
immediately. An hour later he sent for the superintendent. "I think you
had better stop work out there at once, Dan. I should say that the lower
chord here might buckle at any moment. I told the Commission that we
were using higher unit stresses than any practice has established, and
we've put the dead load at a low estimate. Theoretically it worked out
well enough, but it had never actually been tried." Alexander put on
his overcoat and took the superintendent by the arm. "Don't look so
chopfallen, Dan. It's a jolt, but we've got to face it. It isn't the end
of the world, you know. Now we'll go out and call the men off quietly.
They're already nervous, Horton tells me, and there's no use alarming
them. I'll go with you, and we'll send the end riveters in first."
Alexander and the superintendent picked their way out slowly over the
long span. They went deliberately, stopping to see what each gang was
doing, as if they were on an ordinary round of inspection. When
they reached the end of the river span, Alexander nodded to the
superintendent, who quietly gave an order to the foreman. The men in the
end gang picked up their tools and, glancing curiously at each other,
started back across the bridge toward the river-bank. Alexander himself
remained standing where they had been working, looking about him. It was
hard to believe, as he looked back over it, that the whole great span
was incurably disabled, was already as good as condemned, because
something was out of line in the lower chord of the cantilever arm.
The end riveters had reached the bank and were dispersing among the
tool-houses, and the second gang had picked up their tools and were
starting toward the shore. Alexander, still standing at the end of the
river span, saw the lower chord of the cantilever arm give a little,
like an elbow bending. He shouted and ran after the second gang, but by
this time every one knew that the big river span was slowly settling.
There was a burst of shouting that was immediately drowned by the scream
and cracking of tearing iron, as all the tension work began to pull
asunder. Once the chords began to buckle, there were thousands of tons
of ironwork, all riveted together and lying in midair without support.
It tore itself to pieces with roaring and grinding and noises that were
like the shrieks of a steam whistle. There was no shock of any kind; the
bridge had no impetus except from its own weight. It lurched neither
to right nor left, but sank almost in a vertical line, snapping and
breaking and tearing as it went, because no integral part could bear for
an instant the enormous strain loosed upon it. Some of the men jumped
and some ran, trying to make the shore.