last night an Italian of the fill gang was
seen stealing to one of the main foundations, then kicking and tearing
something to pieces. Norton followed him, and found some fuses, and
fragments of paper that had been wrapped about some strange kind of
explosive, which apparently had failed to ignite. The Italian has not
been seen since."

Alex was chuckling. "I think I can guess why that 'strange explosive'
failed to go off, sir," he said. "It was clay." And continuing, he
explained the mystery in detail. Superintendent Finnan laughed heartily.

"Well, Ward, you are certainly due a vote of thanks," he declared
seriously. "You saved the viaduct, and now you probably have brought
about the ending of the entire trouble with the K. & Z. people. I'll not
fail to turn in a thorough report of it."

XXII

THE DEFENSE OF THE VIADUCT

Thanks to the termination of the interference from the opposition road,
the work on the extension progressed rapidly, and two weeks later found
the rail-head seven miles beyond the Antelope viaduct, in the lower
slopes of the Dog Rib Mountains. The coveted pass to the Yellow Creek
gold-field lay but eight miles distant, and as the K. & Z. was still
twenty miles east, it appeared certain that the Middle Western would win
the great race.

The time had passed uneventfully with the three young telegraphers, the
end of the second week finding Alex and Jack together with the
construction-train at the rail-head, and Wilson Jennings back at the
temporary station and material-sidings at the viaduct.

Perhaps the last few days had passed least interestingly with Wilson,
alone in his little box-car station, not far from the old river-bed.
Saturday had seemed particularly slow, for some reason, and shortly after
8 o'clock Wilson threw aside a book he had been reading, and catching up
his hat, made for the door, for a brief stroll, previous to retiring.

The moon was momentarily showing through a break in the cloudy sky, and
looking to the west, Wilson was somewhat surprised to discover the
figures of two men approaching. When as he watched they reached the first
of a train of tie-cars, and leaving the rails, continued forward in the
shadows, Wilson stepped back, in disquiet.

The strangers came opposite, and paused, looking toward the station
window and speaking in subdued voices. Convinced that something was
afoot, the young operator turned quickly, and stooping low, that his
shadow might not