This ultimatum was received with amazement and in dismay shipping circles. It seemed in vain to appeal for armed warships to destroy the "Vorwartz," since she could keep below the surface for days at a stretch, and could descend deeper than any submarine with the exception of the "Aphrodite." And Karl von Harburg believed that his rival was no longer in existence.

There was no doubt that Karl von Harburg was a madman. However successful his raids on shipping might be, however great his h.o.a.rds of ill-gotten gold, he would never be able to make use of his wealth. He was a world-wide pariah. No civilized country would give him refuge.

Even his base in the Island of Sumatra was closed against him, for the Dutch officials, aroused out of their customary lethargy, had seized his concession and had taken strong measures to prevent his return.

Thus, with a crew composed of renegade Germans, Dutchmen, Malays and Chinese, he was compelled to keep to the limits of his submarine until his career of wanton destruction was brought to a close either by an act of G.o.d or the missiles of one of the avenging craft that were ever on the look-out to rid the seas of a scourge.

Meantime Karl von Harburg was directing his attention to the Somali and Zanzibar coasts. Here he could, with little risk, replenish his stock of provisions, while he was within easy distance of the recognized tracks of vessels trading on the East coast of Africa.

"So our sphere of operations is pretty well defined," remarked Captain Restronguet when the message was brought him. "It is not altogether to my liking, for I have some unpleasant recollections of the Somali coast.

Not quite so bad as the West Coast, of course, but quite bad enough."

"You have already visited this coast in the 'Aphrodite'?" asked the sub.

"No; it was in a tramp steamer. We were trading, and instead of getting a profit for the owners we lost half our crew by fever and the bulk of our cargo was seized by the Arabs. That was some years ago. The fever is still there, and no doubt the predatory instincts of the Swahilis and Somalis are as strong as ever. But in a submarine things may be very different."

Once more the quest was resumed, the "Aphrodite" keeping on the surface except when a pa.s.sing vessel was sighted. As secrecy was an essential point Captain Restronguet took no risks, and the submarine was submerged several times during each day.

Early opportunity was taken to thoroughly overhaul the detector, and on taking the sensitive gear to pieces the fault was discovered. It was caused by a thin strand of the insulated copper wire protruding from the amalgam covering and thus setting up a short circuit. In a way that was a matter for congratulation, as it showed that the defect was no way due to magnetic disturbances caused by the heavy thunderstorm, as Captain Restronguet fully expected it to be.

On the other hand the apparatus controlling the potential current of electricity that could instantaneously destroy a hostile vessel by detonating her powder was for the time being beyond remedy. This was a grave business, but the belt of electric fluid that rendered the "Aphrodite" immune from torpedo attack was still in an efficient state.

Had the current been in action when the "Vorwartz" rammed her rival the effect would have been fatal to the former, since, herself a huge torpedo, the submarine would have spontaneously exploded.

Shortly after rounding Cape Guadafui the "Aphrodite" once more came in touch with the "Vorwartz," the detector indicating that the latter was within eighty miles. Two hours later Kenwyn, who was keeping watch on deck, reported that he heard the distinct sound of small arms firing.

Captain Restronguet, Devoran, Hythe, and several of the crew were on deck as soon as they heard the news. The sound was apparently coming from a place about twenty miles to the west.

"That's nothing to do with the 'Vorwartz,' sir," suggested the chief officer.

"I am not so sure about that," replied the captain. "It may have some connexion with that scoundrel Marburg's villainies. We will run in and see what is amiss."

"Submerged, sir?"

"No; on the surface. Time and speed are to be considered."

As the "Aphrodite" came in sight of the coast--a low-lying expanse of sand dunes fringed with a belt of milk-white surf--the hull of a large vessel could be distinguished. Ere long those on the submarine made out that the ship was aground and was heeling at a dangerous angle. She was funnelless, being driven by internal combustion engines. Her masts were still standing, though threatening to go by the board as each sullen roller thrashed against her lofty sides.

Hoisted half way to her mainmast head was the Red Ensign--upside down--as a signal of distress.

Barely two hundred yards to starboard of the stranded vessel was a break in the line of surf and a corresponding break in the coast-line, where either a river gained the sea or the sea formed a narrow inlet. Drawn up on sh.o.r.e at the point formed by the entrance to the creek were three ship's boats, while a quant.i.ty of boxes and casks, apparently thrown overboard from the wrecked vessel, fringed the beach.

On a sandy hillock, standing well apart from the rest of the dunes and within fifty yards of the inlet, were several men in European clothes, who, kneeling behind a shallow embankment of sand, were firing at a foe invisible to the crew of the "Aphrodite."

Three or four had been hit, for they were lying on the sand to the rear of the defences, while, judging by the smoke and the louder reports, the crew of the stranded vessel were being attacked by a far more numerous body of men armed with rifles firing black powder.

"Arabs!" exclaimed Devoran laconically, without removing his binoculars from his eyes.

"Or Somalis," added Captain Restronguet. "Clearly we are in the nick of time, for as soon as it gets dark those fellows will rush the seamen and ma.s.sacre every man-jack of them."

Hythe could not help wondering how the crew of the submarine could render any effective a.s.sistance. The canvas boat had been lost in the encounter with the "Vorwartz," since it was stowed under the midship hatchway.

Captain Restronguet touched him on the shoulder.

"Mr. Hythe, you have had experience with landing parties. I have had none. Will you, then, take charge of our automatic quick-firer? I am sending it ash.o.r.e with nine men."

"Very good, sir," replied the sub unhesitatingly, although he was still at sea as to how the men could be landed.

"Blow all the ballast tanks!" ordered the Captain. "A leadsman for'ard."

Then the sub realized the plan of action. Captain Restronguet was going to take the "Aphrodite" across the bar.

With no more ballast than the two sections of iron bolted to her keel for use in emergencies, the "Aphrodite" drew but five feet for'ard and seven aft. The first soundings gave four fathoms: soon the depth decreased to three.

Yet unhesitatingly Captain Restronguet held the "Aphrodite" on her course, heading towards the smooth patch in the line of breakers that marked the entrance to the creek.

Suddenly the submarine gave a jerk that almost capsized every man on deck. She had stuck right in the centre of the bar, with threatening breakers only a few yards off on either hand.

Simultaneously came a hail of bullets from the opposite bank to which the crew of the tramp steamer were holding. A strong body of Somalis, seeing the helpless state of the "Aphrodite," had commenced to direct a heavy fire upon the stranded submarine.

CHAPTER XXII.

BESET BY SOMALIS.

"Take cover!" ordered Captain Restronguet calmly. "Down below, every man."

The order was promptly obeyed, for several of the leaden messengers were flying perilously close, some impingeing upon the metal sides and conning-towers, that offered a huge target.

"It is as well we afford those rascals something to fire at," he continued, as he entered the fore conning-tower and closed the scuttles on the starboard side. "Otherwise they would be firing into the rear of the position on sh.o.r.e. Serve out the rifles, Mr. Devoran. We must drive them off before we can attempt to land."

So saying the captain ordered full speed astern. For quite five minutes the twin screws ran at their greatest rate, causing the hull to vibrate and the sea to be discoloured with mud and sand churned up by the action of the propellers. Then, with a rasping sound, the "Aphrodite" glided off the bank and gained the slightly deeper water.

"Easy ahead!" This time the submarine was headed slightly to the left of the spot where she had just stranded. Another dull shock told all on board that once more she was held up, this time by her keel.

All the while bullets were flattening themselves against the submarine's plating, but in spite of the danger Hythe thought of something which he immediately put into action. Grasping the lead line he gained the upper platform, ran forward and made a cast. The lead touched bottom at twenty feet.

A bullet cut a gash through the sleeve of his coat, another grazed his shoe, but grimly the sub stuck to his task. Gathering in the line he made his way amidships and made another cast. Here the sounding gave ten feet. He had learnt enough.

"We're nearly over the bar, sir," he exclaimed, as he rejoined his companions in the fore conning-tower. "If we gave her full speed ahead I think she would do it. We're in quite deep water as far aft as the after conning-tower."

Without a word in reply Captain Restronguet telegraphed for full speed ahead. With barely ten seconds' hesitation the "Aphrodite" slipped over the bar and started off up the creek at a great speed till the motors were reversed. Losing way she brought up abreast of the sorry defences held by the shipwrecked crew.

"Here we are, then," exclaimed Captain Restronguet. "But how are we going to get out again? However, that problem can wait. All ready, Mr.

Devoran?"

Under the fore hatchway every available man was waiting, armed with automatic rifles. The field gun was dismounted, in order to facilitate its transport ash.o.r.e, tackles being in readiness to hoist it on deck.