Somehow he bundled him over the rail, and lowered him quickly yet carefully into the boat which fortunately remained where he had left it alongside.

‘Cast off the rope, Pacha,’ he shouted in an agony of impatience, and Othman fumblingly tried to obey.  Ken saw that he would never do it in time, so rapidly made fast his own end to the rail, and giving one pull to tighten the knot, sprang over.

Fifteen seconds more and he would have been safe.  But hardly were his legs over the rail when the explosion came.  There was a stunning shock, the whole ship seemed to melt beneath him.  A blast of hot air struck him, and the next thing he knew was struggling in the water.

For a second or two he felt half paralysed, and as if he could not use his muscles.  He realised that he was sinking, and this gave him such a shock that somehow he managed to pull himself together and strike out.

He came to the surface, dashed the water from his eyes, and the first thing he saw was the dinghy.  By a miracle, she was floating unharmed among a mass of wreckage, but Othman was not in her.

Ken looked round, and saw the old Pacha dangling in the water alongside the swaying steamer.  He was tied to her by the rope of which one end was around his body, while the other was still fast to the ship’s rail.

It was a ghastly fix, for it was clear that the steamer was sinking fast.  Another moment, and down she would go, dragging the unfortunate old man with her and Ken too.  He knew well enough that, as she sank, she was bound to pull him also down into the vortex, and that from this great eddy he would never have the strength to rise.  His one chance for life was to swim away as hard as he could go.

[Illustration:  ‘Ken sprang over.’]

But Ken was not the sort to leave a job half-done.  It was both or neither, and treading water he fumbled frantically in his pockets for his knife.

With a sigh of relief, his fingers closed upon it; he whipped it out, and opening it with his teeth struck out with all his strength for Othman.

It is no easy matter to cut a slack rope with a small clasp knife, especially when the blade is none too sharp.  Ken felt as though he would never get it through.

He heard shouts from the submarine, but could not distinguish words.  The steamer was settling fast.  Already her rail was almost level with the water.

The last strand parted, and dropping the knife, Ken seized Othman, who by this time was quite insensible, and made for the dinghy with all his remaining strength.

He reached it, and got one arm over the stern.  But that was all he could do.  It was out of the question for him to lift Othman into the boat.  He could not even climb in himself.  He was completely done, and could only hang on, panting so that every breath he drew was pain.

From the steamer came the sound of a fresh explosion.  The air, confined below, was forcing up her decks.  Ken knew that now it was only a question of seconds before she sank, knew, too, that escape was out of the question.  The dinghy was bound to be drawn down, and it was not as if the submarine had a second boat which she could send to the rescue.