Greatly to Tressidar's satisfaction, he observed that the airship showed no signs of sinking still more. Apparently the air-tight subdivisions enclosing the ballonets were sufficiently strong to resist the pressure of water. The submerged portion, too, acting as a drag in the sea, prevented the Zeppelin from yawing excessively, especially as the wind was now broad on the port beam.
The chances were that at last a practically undamaged and repairable Zeppelin would be brought into a British port.
A red hue in the eastern sky betokened the dawn of another day with the promise of bad weather. Gradually the beams of the searchlights began to pale before the increasing morning light.
Several miles to windward columns of smoke denoted the presence of the rest of the patrolling craft, which, having abandoned their midnight search, were returning to port.
It was now time for the trawler to alter her course eight points to starboard. She had passed the dangerous area, and could now run parallel with the coast until she reached the entrance to Auldhaig Firth.
Of the Zeppelin's crew not a man was visible. Apparently accepting the inevitable, they had taken shelter from the keen air and driving rain until they were ordered ashore by their captors, there to enjoy the comparatively luxurious life of prisoners of war.
Suddenly the whole fabric of the airship burst into sheets of lurid flame. Shafts of dazzling light shot skywards, mingled with flying debris. Almost immediately came the deafening crash of an explosion, followed by a blast of hot air that swept the torpedo-boat like a tornado.
For a few moments Tressidar was unable to grasp the situation. Where the Zeppelin had been was a dense cloud of smoke, that, caught by the wind, was drifted down upon the sub.'s command until the men were literally gasping for breath. Then upon her decks fell fragments of aluminium girders and wisps of burning fabric that, hurled upwards to an immense height, was beginning to fall in all directions.
The trawler, released from her tow, was forging rapidly ahead, the hawser trailing astern with a succession of jerks. Not until later was it ascertained that several of her crew had been hurled to the deck and seriously injured by the blast of the explosion, while the others were so dazed by the concussion that it was some time before the helm could be steadied and orders given to slow down.
"Rough luck!" muttered Tressidar. "Still, those fellows in that Zepp. had some pluck to blow her up with all on board."