"Yes, sir," nodded the superintendent, from the doorway, and vanished.

"We'll take our leave, now," sneered Hawkins, "unless you have some further humiliation in store for us."

"Just one," Tom declared, "so you can't go just yet."

"Oh, all right," Hawkins laughed fiercely. "You'll have to pay for this unlawful detention."

"You can tell the officers all about that," Tom suggested tantalizingly.

"Mr. Renshaw has just gone to telephone for them."

"The officers? Police?" snarled Hawkins.

"Yes. Did you imagine that you could keep on defying all the laws? You've just threatened me with a taste of the law. You may try a taste yourself, Professor Hawkins!"

"Let us out of this place!" insisted Hawkins angrily. "Come on, friends!"

He rallied his own force of seven men and started toward the door.

"Of course you can try to get away," Reade warned the fellow. "But the effort will cost you all broken heads, to say the least. I have placed you all under arrest for breaking the laws of Alabama, and, before we'll let you go, we'll break a few bones for each of you."

Outside the workmen of the camp were thronging by this time. Doubtless, had they dared, two or three score of these men would have fought in behalf of the gamblers and bootleggers, but far more than that number would have rallied under Tom Reade's banner, for it is human nature to flock to the banner of the leader who is resolute and unafraid. Besides, there were the foremen, all of them good, hard hitting men.

"Oh, well," sneered Hawkins, "let it go at that, Reade. We'll have our day in court tomorrow, and then. I guess we'll find our innings."

"Yes," chuckled Tom, "and when you get your innings you'll be wild to swap them for outings---for the innings will be in jail."

"Don't push my temper too far," cautioned Hawkins with a scowl.

"Let it go as far as you like, always being ready to take the consequences," Tom smiled genially.

There followed a period of tense waiting. After nearly a half an hour of this a 'bus arrived, with four police officers from Blixton in it. Tom Reade preferred his charges against the gamblers and bootleggers. The officers had no choice but to take them, so the late troublemakers, now amid jeers and hoots from many of the workmen, were led outside and into the 'bus.

"You'll hear from this!" hissed Hawkins, in the young chief engineer's ear.

"I believe you," nodded Tom thoughtfully.

After the police and their prisoners had gone Tom led his own party back to the house.

"You'd better get to bed now, Harry," Reade advised his chum. "There can be no telling how soon I'll need to call you up, and you ought to have some sleep first."

"You look for trouble to break to-night?" Harry asked.

"Between now and daylight," said Tom simply.

"Whee! I'd like to stay up with you."

"You might find more fun that way, Harry, but the work to-morrow would suffer, and work is more important than mere fun," Tom answered.

Nor was Tom to be disappointed in his expectation that the worst trouble yet experienced would break loose that night.

CHAPTER XIII

WISHING IT ON MR. SAMBO

"Oho!" breathed young Reade, as he crouched low behind the fringe of bushes, peering toward the beach.

It was now somewhat past midnight. For three hours Tom had been scouting stealthily along this sh.o.r.e section, well to the west of the breakwater.

For, in pondering over the explosions, Tom had come to the conclusion that the blow-outs on the retaining wall, however accomplished, were controlled from a point to the westward of the sea wall.

This conclusion had been rather a simple matter to a trained engineer.

Tom had witnessed the flash of one explosion, and that, as he remembered, had sprung up at the west side of the wall. Moreover, the appearance and condition of the wall, at the point of each explosion, had shown that the attack in each case must have been made at the west side of the wall.

And now, after nearly three hours of work, Tom Reade had come upon a real clue.

"Another blow-out is arranged for to-night, just as I had expected," Reade muttered, with an angry thrill, as he glanced at a figure down on the beach. "Moreover, my guess that the huge negro is the fellow who touches off the blow-outs has proved to be the correct one."

Down on the beach a big, black man was moving about stealthily. Though the spot was a lonely one, this scoundrel plainly intended to take no unnecessary risks of detection.

Just at the present moment the negro was placing in the water a curious-looking little raft that he had brought on one shoulder from its place of concealment. It was something like a flat-bottomed scow, the sides being just high enough to prevent whatever cargo it carried, from rolling off into the water.

The raft placed and secured to the sh.o.r.e, the negro crouched in his hiding place in a jungle of bushes. He soon reappeared, carrying four metal tubes.

"The explosive is in the tubes," guessed Tom easily. "And at one end of each tube is a sharp metal point that permits of being driven into the crevices in the wall. Four, or more, of these tubes are thrust into the wall, I suppose, and connected in series, so that they can be fired by the same electric spark. These tubes and the wires are water-proofed. The negro is only the dastardly workman in this case. It was never he who invented the trick. But he must be an excellent workman, who ought to be employed in much more honest effort. I wonder if the fellow is going to use more than four tubes?"

All of these thoughts ran through the mind of Tom as he crouched, peering eagerly at the negro.

By this time the negro was taking to the water, towing his miniature scow and its explosive cargo as he swam.

"He must be a good swimmer, and also a good diver," concluded Tom. "With my men patrolling the sea wall he must have to dive, some distance away, swim under water, and remain there until he has secured one of the tubes in place. Then he has to get back, out of range of the lanterns' rays, and get his breath before he goes back to the next job. But maybe I can interfere with his work to-night."

Though he rose and moved away, Reade, despite the darkness of the night, was careful to keep himself concealed behind the bushes, so that he could not be observed from beach or water. Shortly the young engineer was over at the point in the jungle from which he had seen the negro emerge with scow and explosives.

"The fellow must use a magneto, attached to wires running under the water,"

concluded Tom. "At that rate, the first real job is to find the magneto.

My, but Mr. Sambo Ebony may be wondering, to-night, why his blow-out doesn't work as easily as usual!"

Simple as the search ought to have been, Tom Reade was soon on the point of despair.

"If it isn't a magneto, or if I can't find it in time," Tom muttered uneasily, "the mystery may remain nearly as great as ever, and the explosion may be pulled off to-night, after all."

Twenty minutes pa.s.sed before Reade, with all his senses alert, stumbled on the concealed magneto. It had been so well hidden, under a ma.s.s of rocks, that it would not have been astonishing had Tom missed it altogether.

Attached to the magneto was the wire that must connect, in some way, with the series of tubes that would soon be fastened in the retaining wall out yonder. Yet this wire ran into the ground, and then vanished.