l's length behind the other.

These railroad torpedoes are small, round tin boxes, about the size of
a silver dollar, filled with percussion powder. To each is attached two
little straps of lead, which are bent under the upper part of the rail to
hold the torpedo in position. When it is struck by the ponderous wheels
of a locomotive, it explodes with the sound of a cannon cracker. The
explosion of two torpedoes, one directly after the other, is the signal
for caution, and bids the engineman proceed slowly, keeping a sharp
lookout for danger. The explosion of a single torpedo is the signal of
immediate danger, and bids him stop his train as quickly as possible. Thus
Brakeman Joe had protected his train by arranging a cautionary signal,
which would be followed immediately by that of danger. Before his train
started again he intended to take up the single torpedo, leaving only
those calling for caution, to show that the freight had been delayed. In
the meantime he decided to walk back to the cars left in his charge and
see that no one was meddling with them.

Rod was too soundly asleep to know anything of all this, nor did he know
when an ugly-looking fellow peered cautiously into his car, and said, in a
low tone: "This here ain't it. It must be the one ahead." The first thing
of which he was conscious was hearing, as in a dream, the sound of blows,
mingled with shouts, and a pistol shot, and then Brakeman Joe's voice
calling: "Rod! Rod Blake! Help! quick!"

An instant later the boy had leaped from the car, and was by his friend's
side, engaged in a desperate struggle with four as villainous-looking
tramps as could well be found; though, of course, he could not judge of
their appearance in the darkness. Joe was wielding the heavy oak stick
that at other times he used as a lever to aid him in twisting the brake
wheels; but Rod was obliged to depend entirely on his fists. The skill
with which he used these was evidently a surprise to the big fellow who
rushed at him, only to receive a stinging blow in the face, which was
followed by others delivered with equal promptness and effect. There were
a few minutes of fierce but confused fighting. Then, all at once, Rod
found himself standing alone beside a car the door of which was half-way
open. Two of the tramps had mysteriously disappeared; he himself had sent
a third staggering backward down the bank into a clump of bushes, and he
could hear Brakeman Joe chasing the fourth dow