And such, indeed, was Lord Hastings’ intention.  The German battleships were so close together that Lord Hastings believed he could strike a double blow successfully and with perfect safety to his own vessel.

Signal flags now were displayed at the masthead of the foremost German battleship and Lord Hastings knew that some answer was expected from the submarine.

“Well, I can’t decipher your signals,” he muttered, “but I can give you some kind of a reply—­which I don’t suppose will be much to your liking.”

He turned and gave a command to Jack; and Jack, in turn, flashed it upon the electric signal board below with the pressure of a button beneath his finger.

“Attention!” came the command now, displayed in letters of fire.

Then a brief lapse of time, in which all was silence below.

Then another signal showed red on the board.

“No. 1 torpedo!  Fire!”

Again came that faint metallic click to which the boys had grown so accustomed, and a terrible engine of destruction sped over the water toward the German ships.

A moment later a second command flashed on the board.

“No. 3 torpedo!  Fire!”

Once more the click and then nothing but silence.  A moment later Lord Hastings hurried below.

“Submerge!” he ordered.

CHAPTER XXII.

TOWARD OSTEND AGAIN.

Jack had been ready for this command and repeated Lord Hastings’ words immediately.  Not a second was lost, and a moment later the tanks began to fill and the submarine sank lower and lower in the water.

Jack, who had glued his eye to the periscope, gazed at the German battleships as long as it stayed above water.  In the few moments that it took the craft to submerge, he saw that two of the enemy’s craft had been struck and that the other two had trained their big guns upon the U-6.  His heart beat fast, for he was afraid the submarine would be unable to put a thick enough blanket of water above it to withstand the German shell, should the first shot be gauged accurately.

Just before the periscope disappeared beneath the surface, cutting off the lad’s view, he heard the faint sound of a gun.  He braced himself for the shock that he expected; but none came.  The first shell had gone wide and he breathed easier.  Before the second shot came, the U-6 was safe in the depths.

“Pretty close,” the lad muttered aloud.

“What was pretty close?” demanded Frank, who had not heard the sound of the shot.  “Didn’t we hit either one of them?”

“Oh, yes, we got them both,” replied Jack.  “I was talking about our own escape.  The Germans fired one shell at us and they can’t have missed very far.  Fortunately, we came down before a second.”

“Shape your course due east, Mr. Templeton,” commanded Lord Hastings at this juncture.  “We’ll have a try at another of them.”