Moreover, now that the big black was a prisoner the men would hardly be needed on the wall.
"I think I know just how Sambo worked it, too," the engineer reflected, as he ran.

"He swam out into the Gulf, towing that little scow behind him.
Neither his black head nor the little scow would be seen far on the water on a dark night.

Sambo, when he got near enough, could take one of the metal tubes, swim in under water to some point where no watchman was near, and stick the tube fast into the wall.

Then another tube, and another---all under water where they would not show to a passing watchman.
"Then, when he had all in place, and while no patrolling watchman was too near, Sambo could begin to attach the wires.

That would take but a few minutes.