“You’ve had treachery aboard, have you?” asked the lieutenant commander, as he climbed up over the side.

“Rather.  A new machinist, taken aboard just before we sailed from Dunhaven.  The same fellow who must have played the trick on the ‘Pollard’s’ engines yesterday,” Benson replied.

“I’ll be glad to have a fellow like that in irons in the brig aboard the ‘Hudson,’ then,” muttered Mr. Mayhew.  “I couldn’t understand, Mr. Benson, how you were doing so badly in the full speed ahead dash.”

“The prisoner below is the answer, sir,” Captain Jack replied.  He then led the corporal and two marines below.  The corporal produced a pair of handcuffs, which he promptly snapped over Truax’s wrists.

“You’ll be sorry for this, one of these days,” threatened Truax, with a snarl that showed his teeth.

“Some day, then, if you please, when I have more leisure than I have now,” Jack retorted, dryly.  “This man is all yours, corporal.”

Truax was foolish enough to try to hang back on his conductors.  A slight jab through the clothing from one of the marines’ bayonets caused the prisoner to stop that trick.  He was taken on deck and over the side.

“Coxswain, return for me after you’ve taken the prisoner to the ‘Hudson,’” directed Mr Mayhew.  “Now, Mr. Benson, I would like to see what has been done to your engines.”

“That’s just what I want to know, too,” responded Jack.

They found Hal and Williamson hard at work, inspecting the motors.

“The ignition power was lowered, and that may have been the most that the fellow did,” said Hal.  “Yet, at the same time, before putting these engines to any severe test, I believe they ought to be cooled and looked over.”

Lieutenant Commander Mayhew frowned.

“These delays eat up our practice cruise time a whole lot,” he grumbled.

“I’ll put the engines through their paces, and chance mischief having been done to them, if you wish, sir.”

“No; that won’t do either, Mr. Hastings,” replied the naval officer.  “This craft is private property, and I have no right to give orders that may damage private property.  I’ll hold the fleet until you’ve had time to inspect your engines properly.  By that time, however, we’ll have to put back to the coast for the night, for our practice time will be gone.”

“In the days to follow, sir,” put in Benson, earnestly, “I think we can more than make up for this delay.  We won’t have the traitor aboard after this.”

“What earthly object can the fellow have had for wanting to damage your motors?” demanded the naval officer, looking hopelessly puzzled.

“I can’t even make a sane guess, sir,” Jack Benson admitted.

An hour and a half later the “Hudson” and the two submarines headed back for a safe little bay on the coast.  Here the three craft anchored for the night.

CHAPTER XVII