Whenever any one came too near Sambo had but to swim out a little way and tread water until he could return to his job.

When, at last, all was complete, Sambo would attach a wire from the bombs to a wire moored at a stated point under water, and then swim in, work his magneto, and touch the whole thing off from a safe hiding place on shore.

The explosion itself would shatter the last length of wire.

Oh, but it was all slick and easy!" Not increasing his speed, but keeping steadily at the jog-trot, Tom was at last near enough to the wall to raise his voice and shout.
"Hullo!" came back the answer.
"This is Reade, the chief engineer," Tom answered, through the night.
"We've caught the fellow that has been blowing up the wall.

A half a dozen of you men hurry over here with your lanterns.