"Look out!" he shouted.
Instantly the air and sea together were torn by a terrific crash, which must have been heard a score of miles away. In that instant Mark saw the whole fabric of the trawler burst open. The boat heaved under him, and he was flung forward, stunned and unconscious.
CHAPTER III.
WATCHERS OF THE SEA.
The sound of that explosion carried its warning far over the fishing grounds of the Silver Pit. It reached tramps and colliers plying their ceaseless traffic along the coast. Nearer at hand it alarmed the crew of the trawler Mignonette, who saw the column of smoke and wreckage shot skyward as from the crater of a volcano, and who, regardless of their own danger from floating mines, hastened to the spot to pick up the dazed survivors huddled together in the open boat. It reached the officers and men on a patrol of destroyers speeding northward within sight of the English shores. On the cruiser Atreus it was distinctly heard, coming like a challenge across the waves.
"Oho!" exclaimed the astonished commander, arresting his pacing of the quarter-deck. "Gunfire, eh? Hostilities are opening even earlier than we expected!"
He stood by the binnacle, listening for a second "boom."
"Seemed to me almost more like the explosion of a contact mine than a gun, sir," ventured the signal lieutenant, halting beside him.
"A mine?" protested the commander. "No, no, impossible! We have laid no mines. It is not in our programme to lay mines; and certainly not on the high seas. The enemy cannot have laid any, either—not over here; not so promptly, hardly thirty hours after the declaration of war. It cannot have been a mine. And yet there was only one detonation. If it had been a naval gun, it would have been answered. However, we shall soon know. We must go and see. Send out the signal to change course eight points to starboard."
It chanced that Rodney Redisham was midshipman of the watch, and that it fell to him to help in transmitting this signal.