The periscope was now above the surface and his eyes were upon the image of his target reflected in the mirror. He was taking aim, manoeuvring the submarine into position as if she herself were a gun. For some tense moments all was quiet but for the purr of the motor and the working of the air-compressors for charging the torpedo-tubes. Then there came a thumping sound as of a heavy door being shut. This was repeated. Two torpedoes with their mechanism adjusted had been thrust into the breach of their tubes. Mark would have given much to see how it was done. But he did not dare to move. Obeying the recommendation to make himself small, he waited breathlessly.
"Number one—fire!" came the sharp command.
There was a violent gush as a torpedo was discharged on its errand of destruction. The whole vessel shuddered and was alarmingly unsteady until the compensating-tanks were filled and the true balance was regained. Then a second torpedo was fired. Mark listened, wondering, as the submarine dived with her nose down, if either of her weapons would strike the target at which it had been aimed. They had been fired at long range, but their rush through the water was quickly over. A low, rumbling explosion told that one of them had struck and burst against the German cruiser’s bilge.
The H29 remained deeply submerged, her electric motor driving her forward at ten knots speed for something like a quarter of an hour, when once more the water was blown from the tanks and she rose to bring her periscope above the surface.
The sub-lieutenant was now in the conning-tower with the commander.
"We got her under the forward magazine," Mark heard Lieutenant Ingoldsby announce. "She’s sinking by the bows. The German collier that we saw yesterday is standing by, picking up survivors. She’s fitted with wireless, so we may as well keep out of sight. Carry on just as we are for another half-hour, Desmond, and shape a course for Haddisport Roads."
"Yes, sir," returned Mr. Desmond. "And what about our mine-sweepers?"
"Oh, they are all right!" the commander signified. "I’ve just counted them. I don’t believe any of them was hit. Lucky for them that we turned up. She’d have sunk the lot."
"We’ve got one of the crew of the _Dainty_ aboard of us, sir," the sub-lieutenant told him.