"Aye, aye, sir."

There followed several minutes of tense waiting, the rhythmic "clank!"

"clank!" of the apparatus that supplied the diver with fresh air being the only sound save the lapping of the water to break the stillness.

"He's found the mine, sir," called the diver's a.s.sistant.

"Very good. Davis, signal the ship that we have located the mine."

Dan stood up, flashing the message through with a few swift dips of the signal flag. Sam wondered how they knew the man, Kester, had found what he was in search of. What he did not know was that the men in the other boat were able to hold a limited conversation with the diver by means of a signal rope, certain jerks meaning certain words or questions.

"The mine is secured, sir," called the a.s.sistant.

This meant that the diver had succeeded in making fast to the lost mine one of the ropes that he had taken down with him.

"Shall we raise the mine first before getting Kester up, sir?"

"By all means. He has not asked to be brought up, has he?"

"No, sir."

"Haul away, then, lads."

A warning signal was sent to the man below, after which the a.s.sistants in the boat began pulling and tugging at the rope attached to the mine.

Evidently the mine was imbedded in the sandy bottom, for it refused to move, the men jerking this way and that to free it from its resting place.

All at once it did come away, and with a suddenness that caused the men to sit down in the bottom of the boat, losing control of the line.

"Clumsy! Look out or you will lose it again," cautioned the ensign.

Quickly pulling themselves up, they began hauling in on the line. Very slowly the sphere moved upward, at last appearing above the surface of the water, shining and almost menacing Dan thought as he gazed at the object.

"Now be careful in getting it over the side," warned the officer.

The diver had put what he considered to be a strong hitch on the mine with the end of the hauling rope. On account of the depth at which he was working, however, the darkness compelled him to operate solely by the sense of feeling.

The mine was now swaying on the gunwale of the rolling small boat, the waves from the rising sea breaking over into the cutter as well as into the other boat, until the men were standing in the salt brine.

"Look out! There she goes!"

With a great splash the mine struck the water, having slipped its lashings, and quickly sank out of sight.

"Warn the diver!" shouted the ensign.

A jerk on the signal cord conveyed the message that the mine was falling toward him.

"Does he answer?"

"No, sir."

"Quick! Give him another warning!"

"He does not answer, sir."

"There goes the signal line! It's fouled, sir!"

A violent wrench on the supporting line with which the diver was to be hoisted to the surface tore it loose from its fastening on board the diver's boat.

"The line's gone, sir!"

All hands were standing up in the rocking boats. The sky had suddenly become overcast and spray was dashing over them in blinding sheets.

Sam stood as if dazed. He did not catch the full significance of the scene, but his mind was working. Like a flash it dawned upon him.

"There goes the air tube. That settles him, sir!"

"What does it mean?" stammered Sam.

"The diver is drowning three fathoms under the sea. Nothing can save him," groaned some one.

An instant of silence followed.

Dan threw up his flag signaling, "accident."

Then a body flashed through the air. The dazed spectators caught sight of a white service uniform, as the intrepid Dan Davis plunged into the sea, disappearing beneath the waves.

Sam's flagstaff struck the gunwale with a bang an instant later, toppled over and was quickly carried away. Ere it had reached the water, however, the second Battleship Boy had leaped to the bow of the boat and before they could utter a word of warning, he had followed his chum Davis with a long, clean dive into the ocean.

CHAPTER XXIII-HEROES TO THE RESCUE

"Men overboard from the wherry!" bellowed a voice in the motor boat that had brought out the second diving suit.

"Stand by to pick them up!" roared the ensign.

"They'll never make it. Shall we go over, sir, and help them out when they come up?" asked a seaman.

"Stand by! Not a man of you goes over. You couldn't live in this sea.

The fools-to do a thing like that!"

The wind had increased to a gale, great walls of water hurling themselves against the frail craft and breaking over them in quick succession.

"Bail boat," commanded the ensign.

"Aye, aye, sir."