Even Dastral's face was pale, though not with fear, as he jammed the rudder bar over with his feet, and using the joy-stick as well, came round swiftly once more, dropping down to within fifty feet of his enemy.
"Great Scott! She's preparing to submerge, Jock. For heaven's sake don't miss her this time!"
Jock did not reply, but taking true aim just as they were directly over the boat, he dropped his second and last bomb fairly and squarely on the conning-tower.
"Whis-s-s-h! Boom-m-m!" came the sound as the bomb descended swiftly and exploded right amidships, splitting the conning tower open, just as it was being closed ready for the boat to descend.
A blinding sheet of flame shot up into the sky, scorching both the pilot and the observer, and a crashing noise followed the explosion, as the submarine, her deck split open and rent in twain, opened out, then sank like a stone, carrying down with her the twenty-two men who manned her.
A few minutes afterwards the only trace of the pirates was an ever-extending patch of oil which floated on the surface of the water, punctured here and there by the air bubbles which forced their way through the patch.
So suddenly did she disappear from view that even the airmen, scorched and bruised and bleeding from slight shrapnel wounds, were amazed at the work of their hands. Dastral was the first to recover speech, however.
"Well done, Jock!" he cried. "Thus may all pirates perish who fire on the Red Cross flag."
The observer did not reply, however, for he had fallen forward in a dead faint, from sheer excitement and loss of blood; perhaps most of all from sheer fear of failure with his last bomb. And now his head was resting against the wind screen just in front of the cockpit.
"Jock! Jock! What's the matter?" Dastral called to him.