rls itself upon the track. Even the echoes of the locomotive
whistle will in some states of the atmosphere bring disaster. Tiny snow
crystals are jarred by the sound-waves; these start on a downward
career, gathering volume and speed until a mighty avalanche has been
developed.

In one of these mountain canyons lives a Scotch track-walker and his
only companion, a beautiful and intelligent collie dog, who always
accompanies his master on the inspection rounds.

It was in the late afternoon of a strenuous day in May, when Jock and
Collie arrived weary and hungry at the 'shack' (hut) door. Everything
was satisfactory in the canyon, the section gang had gone down the
track, and with a sigh of content Jock set about preparing his evening
meal. Collie, with his head between his paws, watched the proceedings.
Suddenly he assumed an alert, listening attitude, then he set off at a
great rate up the track.

When supper was ready Jock whistled for his companion, and on looking
out was surprised to find him gone; but from the narrowing walls of the
gorge came the sound of his furious barking. Jock whistled again and
again, but the dog did not come. Perfectly convinced that something was
wrong, he seized his rifle and hurried off, expecting to find that
Collie had cornered some wild animal, or that some animal had cornered
him! Round the curve he hurried, and what he saw almost paralysed him.

A great boulder, weighing many hundredweight, lay across the track, and
on top of it, wild with excitement, was Collie.

On the little flat near the 'shack' was the switch at which the Pacific
and Atlantic Expresses--the trains going East and West--crossed. They
were due almost at once. He was alone, time was short, and upon his
action depended the safety of many lives. He could not go both ways at
once with his warning; but down the western track beyond the switch he
sped with explosive 'torpedoes,' or detonating signals. Then he hurried
back again past the dog (still on his signal station), and far to the
east, round the long curve, with his red flags of danger.

The express from the Pacific, warned by the torpedoes, steamed slowly,
very slowly, to the switch, then came to a standstill.

The train crew ran down to the hut, which was thick with smoke from
burnt 'flap-jacks' and frizzled bacon, but found no sign of Jock or
Collie. Round the curve they ran, and there, still on the boulder, was
Collie, barking, as the brakeman expressed