“Eh?  What is it?” called Jack, almost instantly.

“You’re wanted on deck, Captain—­instantly,” replied the dripping machinist.

“Oh, all right, Williamson,” and Benson’s feet hit the stateroom floor.

A minute later he was above, Hal following only some twenty seconds behind his young chief.

Williamson swiftly told how he had heard the bumping against the hull, and how he had found the cylinder, with a wire connection.

“Gunboat, ahoy!” roared Captain Jack, snatching up a megaphone and holding it to his lips.

The response was prompt.  In less than three minutes a cutter, containing an officer, a corporal and four marines, was alongside.

“The first thing for us to do is to take that cylinder aboard the ‘Waverly’ and investigate it,” decided Ensign Foss.  “I’ll leave the marines here until I get further instructions from the commanding officer.”

“Anything happening?” demanded Eph, reaching deck just after the cutter had put off.  He eyed the marine squad curiously.

“Just what we’re trying to find out,” replied Jack.

“It must seem to you that I acted amiss in leaving the deck,” put in Williamson.

“But you didn’t,” retorted Jack.  “Had you been on deck you wouldn’t have heard that infernal machine bumping against the hull.”

“Infernal?” echoed Eph Somers, rubbing his eyes.  “Say, have I been missing a whole lot by being asleep?”

The other three told him quickly all they knew of what had happened.

Within five minutes the cutter came back, bringing two more marines and a young second lieutenant of that corps.

“Lieutenant Commander Kimball’s compliments, sir,” reported the second lieutenant.  “He will put in an appearance as soon as that cylinder has been investigated.  He has sent me with instructions to see what had best be done.”

“I don’t believe there’s much doubt as to what had best be done,” replied Captain Jack, quickly.  “Williamson reports having cut a wire that was attached to that cylinder.  I think we can find that wire again, and, if we do, we can easily follow it to its other end.”

“By jove, that’s good enough,” muttered the lieutenant.

“Williamson is already wet,” proposed Jack.  “He can dive again, and see whether he can pick up that wire.  If he needs any help, I’ll go overboard with him.”

“Wait until I see what I can do,” proposed the machinist.

This time he dived over the port side of the craft.  Three or four times he came up for air, next going, below again.  At last, however, Williamson came up, calling: 

“I have a part of the wire in my hands.”

Lieutenant Foster ordered his marines into the cutter, inviting Jack and Hal also to go with him.  They rowed out alongside of Williamson, picking up the machinist and his wire.

“We’d better put your man back on the boat, hadn’t we, Mr. Benson?” inquired the marine lieutenant.