pair of nippers, thrust them
into his jumper and raced up to the deck.

"If it's any real mischief," he muttered, "I hope I won't be too
slow--too late!"

With that he dived overboard, at the starboard rail, the side nearest
the gunboat. There was a splash--then the waters closed over the
machinist.

He came up at about the point he had planned, where he had heard the
bumping.

Held below water as he was by the under-hull of the submarine, he could
move with certainty, though but slowly.

Groping, the machinist encountered the metal cylinder. Quickly he felt
for its connections which, like a flash, he knew must exist. He found
the wire, but reached for another. It all had to be done swiftly, for
his reserve "wind" was fast giving out. Not finding a second wire, he
fastened his nippers against the first wire--then cut. Now, steering
the metal cylinder, he pushed it out from under the hull. Cylinder and
man rose together.

Whew! What a powerful breath the man took! Then he steered the cylinder
carefully against the hull, and managed to hold it there until he could
reach a piece of cordage and make the cylinder fast.

This done, he dashed below, thumping hard on the door of the stateroom
occupied by Captain Jack Benson and Hal Hastings.

"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 de