Finally he compromised the difficulty. Kenwyn was to be isolated from the rest of the crew, Mylor and Lancarrow volunteering to act as nurses, until the "Aphrodite" entered the gorge through which the Zambezi flows. Here the patient was to be landed, placed in a tent and left in charge of the two men till the "Aphrodite's" return.
Just below the town of Kaira, where the Shiré River joins the Zambezi, definite news came to hand concerning the "Vorwartz." A large canoe, laden with millet, arrived the same day as the "Aphrodite." Her crew reported, through a Portuguese interpreter who spoke indifferent English, that they had passed a strange-looking vessel, somewhat resembling the "Aphrodite," four days up the river, and that it was hard aground at the mouth of a tributary known as the Zampa.
This report was confirmed by the detector which gave the "Vorwartz's" position as sixty-three miles to the north-west. Captain Restronguet noticed that he was gaining rapidly on his rival, and had been unable to account for the rapid decrease in the intervening distance unless Karl von Harburg had lighted upon an isolated spot that seemed to suit his requirements.
At Kaira Captain Restronguet was able to procure an old though fairly reliable Portuguese map of the course of the river, and on this the position of the rival submarine was carefully noted. If she succeeded in floating and proceeding up the Zampa River it was evident that the "Vorwartz" would soon be in British territory--the colony of Rhodesia.
That same evening a wireless message--the first for three days--was received from Captain Restronguet's English agent stating that the Foreign Office was in communication with the government of the Portuguese Republic, and an arrangement had been arrived at whereby three British sternwheeler gunboats that were used to patrol the Shiré River, were to be allowed to descend to the Zambezi and attempt to cut off the "Vorwartz" on her return.
"Evidently the British Navy wants to chip in at the death," commented Captain Restronguet. "We must look to our laurels. It would be hard lines to be searching for days amongst these unexplored backwaters without success, and to find that one of these little paddle-boats by a piece of sheer good luck had managed to blow the 'Vorwartz' to smithereens while she was lying helplessly stranded on a mud-flat."
Hythe did not reply. He was naturally anxious, now that he had been on board the "Aphrodite" for such a lengthy period and had faced perils in company with her crew, that Captain Restronguet should receive a just reward for his strenuous endeavours; yet he did not forget that he was still an officer of the great British Navy, whose policy is to be ready, aye ready, in the hour of triumph or in the hour of disaster alike.
Just then Carnon, who since Kenwyn's illness had been appointed solely for duties in connexion with the detector, approached and saluted.
"The detector, sir, has gone wrong," he reported.
"Gone wrong? What do you mean? Have you been tampering with the instrument?"
"No, sir. The last reading gave sixty-one miles. That was five minutes ago. When I looked again there was no record at all. The batteries are still working: I could get a spark an inch in length. The terminals are properly clamped."
Captain Restronguet, Devoran, and the sub hastened to the compartment in which the detector was fixed. The indicator board was absolutely blank.
"We're not having an easy time of it at all," remarked the captain. "Without the detector it is quite possible that the 'Vorwartz' may yet outwit us. All the same, I cannot understand it."
"We know her position up to ten minutes or a quarter of an hour ago, sir," said the first officer.
"Quite so, Mr. Devoran; and we must work on that. It will take us three hours, running at the highest speed compatible with prudence in this brute of a river, to arrive at the spot where the 'Vorwartz' was last reported. In three hours Karl von Harburg may have shifted a long distance off--or he may not."
"And there's Kenwyn to be taken into account."
"I haven't forgotten him. I think after all we had better keep him on board. It is too much of an undertaking for two men to have and tend him, provide for themselves, and be on their guard against the wild animals that abound, and a dozen other difficulties that a camp on shore would entail. However, pass the word for a speed of twenty-four knots. Allowing for the adverse current we ought to be at the confluence of the Zampa River well before sunset."
Just above the town of Shemba the Zambezi bifurcates, the two streams reuniting twenty miles higher up. It was just possible that the "Vorwartz," bound towards the sea, might be passing down one branch while the "Aphrodite" was proceeding up the other; but this time luck was in Captain Restronguet's favour, for above the junction the "Aphrodite" fell in with a trading steamboat, whose captain, by signs, made it clear that no vessel of any description approaching the "Vorwartz" had passed down the left-hand stream.
The river here was considerably narrower and deeper than nearer its mouth. Its width was still over half a mile, while the soundings gave a level bed of six fathoms. Here, also, the tide was no longer felt; but, owing to a cessation in the rainfall, the level of the river was gradually sinking.
During the course of the day several canoes passed at a respectful distance; but late in the afternoon a craft of some sort was sighted drifting down in mid-stream.
As the "Aphrodite" approached it was seen that the object was a raft composed of several slender spars supported by four barrels, to which were lashed four or five short planks. Lying on the platform thus formed were two human bodies.
"What do you make of it, Mr. Devoran?" asked Captain Restronguet. "A tragedy--not exactly on the high seas--but one of a very extraordinary nature. They look like Europeans."
"Shall I have the boat lowered to investigate, sir?"
"No, they're dead right enough. I've been watching them pretty carefully through my glass for some time. If it's a case of contagious disease we had better sheer off."
"Why, they're Chinese!" exclaimed Hythe.
"Chinese? Then they must be some of the crew of the 'Vorwartz'," said Captain Restronguet. "Evidently von Harburg has met with disaster."
As the submarine passed the aimlessly drifting raft a fairly close view could be obtained of the dead Chinamen. They were dressed in blue cotton suits after the style affected by Chinese seamen serving in European vessels, but there was no mistaking the Tartar features and the slanting eyes. That they were stone dead there could be no doubt, for there were several birds hovering around the raft in a manner that their natural timidity would not permit if the two bodies showed signs of life.
"Do you think that a catastrophe has occurred to the 'Vorwartz,' sir, or were these men merely attempting to escape?" asked the sub.
"Coupled with the fact that our detector has failed to give any indication of the 'Vorwartz,' I am inclined to favour the first theory," replied Captain Restronguet. "Since our apparatus is, as far as I can tell by careful examination, in perfect working order, I can only put its unresponsiveness down to the failure of the electric current on board the 'Vorwartz.' That, of course, would account for the failure of our detector."
"And the 'Vorwartz' could otherwise be capable of action?"
"To a certain extent. But without electricity she can have no means of compulsion, no means of offence, unless we except the use of fire-arms. However, before to-morrow is past we ought to discover her whereabouts. I am not proceeding further to-day as night is approaching. As soon as we find a suitable depth we'll descend till morning."
Another night passed without interruption. The detector was still silent, but the "Aphrodite" was now within a few miles of the spot where the "Vorwartz" had last given notice of her presence.
It was not a desirable day. Torrential rains were falling, while the atmosphere was too close to wear oilskins without the greatest discomfort. Consequently on the "Aphrodite" rising to the surface her crew save three had to remain below.
Captain Restronguet, Hythe, and Carclew were in the for'ard conning-tower, Devoran, Carnon the quartermaster, and Polglaze occupied the after conning-tower, so as to maintain a careful look out on all sides. Three men, braving the heavy downpour, were stationed for'ard, where they took turns in casting the lead.
The river here was considerably narrower--about thrice the width of the Thames at London Bridge. The banks on either hand were low and densely covered with thick scrub and extensive forests of tropical trees; while the skyline was broken on both sides by serrated ridges of lofty mountains.
"This must be the Zampa River," said Captain Restronguet, pointing to a fairly wide waterway that joined the Zambezi on its right bank. "Here the 'Vorwartz' was sighted by the natives. It would be well to explore the stream before going further."
"It looks too shallow to take anything more than a flat-bottomed light-draught vessel," remarked Hythe. "Still, as you say, sir, we ought to leave nothing unexplored behind us. If you wish I will take charge of the whaler and see what it is like."
"Very good, Mr. Hythe. I shall be obliged if you will. We'll remain here. Do not proceed further than there is depth for the 'Aphrodite' to follow. Should you require assistance fire three explosive rockets. If anything should necessitate your immediate return I will make a similar signal. Should you locate the 'Vorwartz,' endeavour to return without being seen."
It certainly required plenty of zeal to volunteer for a boating expedition on a tropical river in such torrential rains, but the men called upon for the service responded with alacrity.
Four rowers stripped to the waist sat on the thwarts, apparently quite indifferent to the rain. Hythe, Polglaze, and Carclew were in the stern sheets, partially protected by an awning, but before the whaler pushed off the canvas covering, sagging under the quantity of rain water, was found to be of more trouble than use, for a regular stream poured through the canopy upon the sub's head and shoulders. Since it was also likely to attract the attention of Karl von Harburg's men Hythe ordered it to be struck, and accepting the situation as well as he could, was soon soaked to the skin.
The tributary was found to be nearly twenty feet deep towards the right-hand bank. On both sides were belts of malodorous mud on which numerous crocodiles were lying as if enjoying the rain. Others, looking more like floating logs, were drifting in the channel, and careful steering was needed to avoid them. Hythe realized that he was not on a sporting expedition, and should any of the saurians become infuriated it would be necessary to fire at the reptile. The report of the rifle would give the alarm to the "Vorwartz" should she be within hearing, and the chances of locating her without being discovered would be very remote.
For more than a mile the rowers toiled manfully. The current was strong, the boat heavy, while Polglaze had to bale incessantly to prevent the rain from rising over the stern gratings. The "Aphrodite" was now lost to view by an intervening bend in the course of the stream.
The depth still continued regular, and afforded plenty of water for a craft like the "Vorwartz" to ascend if her ballast tanks were emptied, but as reach after reach was opened out no sign of the rival submarine was visible--only a monotonous stretch of coffee-coloured water enclosed on either hand by the soft stagnant mud that effectually prevented any attempt at landing.
"What's that, sir?" asked Polglaze, suddenly holding up his hand and listening attentively.
"Lay on your oars, men," ordered the sub.
Above the hissing of the rain Hythe could distinguish the deep purr of a powerful motor. Could it be that the "Vorwartz" was returning? If so, escape was impossible, for no cover of any sort was obtainable, and long before the whaler could return to the "Aphrodite" she would be overtaken by the swiftly moving submarine.
"It's that brute of a von Harburg coming downstream, sir," exclaimed Carclew. "We're fairly trapped."
In reply the sub ordered the boat to be turned and her head pointed down stream. Drawing the three detonating rockets from a locker under the stern sheets he rapidly lashed the sticks in position. Happen what may the "Aphrodite" must have warning of her enemy's approach. Perhaps, as the "Vorwartz" was now under way her electrical current would operate the detector onboard the "Aphrodite"; if so there was every reason to suppose that Captain Restronguet was already on his way to rescue his whaler's crew and engage his sworn foe. A chance of safety yet remained.
"Give way, men," ordered Hythe. "We may do it yet."
Nearer and nearer came the throb of the powerful motors. Hythe grasped the lanyard of the nearest rocket. He hesitated. There was something in the sound of the motors that could not be associated with a submarine, even allowing for the conductive properties of the water; it was more like the drone of an aerial propeller.
The next instant the snub nose of a large airship appeared round the bend of the river. The vessel was flying low; her two suspended cars were not forty feet above the surface. Her yellow silk envelope was literally streaming as the rain descended upon it in torrents, and this was why, Hythe reasoned, she was flying so low.
The sub ordered the whaler's crew to cease rowing and soon the airship was overhead. Her engines were reversed, and losing way she brought up just in front of the boat. Hythe saw with feelings of relief that aft the airship was flying a Blue Ensign with a yellow propeller--the badge of the recently constituted British Empire Aero-League--emblazoned on the flag. Half a dozen men were leaning over the rail of the platform connecting the two cars.
"What boat is that?" hailed a tall, sparsely-built man dressed in a white uniform.
"The 'Aphrodite' submarine, Captain John Restronguet," replied Hythe without hesitation. "What airship is that?"
"The 'Pride of Rhodesia,' of Salisbury. Is Captain Restronguet in the boat?"
"No," replied Hythe. "He is on board the 'Aphrodite' lying at the junction of this river with the Zambesi."
"And who are you, sir, might I ask?"
"Arnold Hythe, Sub-lieutenant of the Royal Navy."
"So you are the Mr. Hythe we've heard so much about? Glad to meet you. Sorry we can't shake hands; must delay that honour till a more convenient time. I'm Jones of Salisbury, Rhodesia, and we're having a chip-in with that villain, Karl von Harburg. I suppose we are not too late?"
"Seen anything of her?" asked Hythe. "We are exploring this river in the hope of finding her brought up."
"May as well give it a miss," replied Captain Jones of the "Pride of Rhodesia." "We've followed the whole of the navigable part of this ditch. We've also reconnoitred the Mali, the Tutti, and the Baraloo; the Zampa we didn't trouble about; it's too narrow to take a craft the size of the 'Vorwartz.'"
The sub felt like shaking hands with himself. The airship had purposely overlooked the river in which the "Vorwartz" had been reported. Captain Restronguet had made a mistake in thinking that this river was the Zampa.
"Well, I wish you luck," he said truthfully, for there can be various qualifying conditions to the subject of luck. "By the by, what's the name of this river?"
"The Pongo," replied Captain Jones. "It rises in Rhodesia not so very far from the frontier of the Portuguese territory. I reckon we've saved you a bit. We'll save you more yet if you wish. We'll tow you down stream. I'm curious to see the renowned 'Aphrodite.' Captain Restronguet won't object, I suppose. Will you come aboard--we'll drop a rope-ladder."
"No, thanks," replied Hythe. "We won't come on board. We cannot get much wetter if we stay here. All the same, we shall be glad of a tow."
The sub was cautious. He did not wish to be kidnapped a second time, and not knowing who Captain Jones was or whether the "Pride of Rhodesia" was a bona fide craft belonging to the British Empire Aero-League, he thought it advisable to decline the invitation to board the airship.
A coil of rope whizzed from the after platform of the overhead vessel. It was caught and made fast by the bowman, the "Pride of Rhodesia's" huge propellers began to revolve and soon the "Aphrodite's" whaler was being towed down the stream at a good ten knots.
"Pass that rope aboard the 'Aphrodite,' please," shouted Captain Jones as he brought the boat alongside the submarine. Captain Restronguet waved his hand in token of assent and soon the airship was riding head to wind with her nacelles just resting on the water.
Hythe hurriedly explained the circumstances under which he had fallen in with the airship, mentioning that he had found out by accident that it was not the Zampa River that he had explored after all.
"That's good," commented Captain Restronguet enthusiastically. "We can well afford to be disappointed. This Captain Jones told you he didn't mean to explore the Zampa, eh? Well, we'll have him on board, since he evidently desires it, but we must be careful not to drop the faintest hint concerning our information that the 'Vorwartz' was known to have entered that river."
The boat was dispatched to bring Captain Jones on board the "Aphrodite," and soon the owner and commander of the "Pride of Rhodesia" stood upon the deck of the submarine. He was a fairly young man, still under thirty, and full of almost boyish enthusiasm.
"We seem to be sort of friendly rivals," he remarked. "I don't want to boast, but I think I stand the better chance. Had that German scoundrel kept to the sea the odds would be in your favour, but since he is in comparatively limited and shallow waters he cannot submerge his 'Vorwartz.' But aloft I can command a vast extent of country, while you have to grope about, if I may say so."
"I quite see the point of your argument," replied Captain Restronguet drily. "But, might I ask, what do you propose to do when you find the 'Vorwartz'?"
"Oh, we are armed," said the Captain of the "Pride of Rhodesia." "We carry two bomb-dropping devices, besides four quick-firers. We are subsidized by the Government and authorized to carry offensive and defensive weapons. Directly we spot the 'Vorwartz' I shall have no hesitation in dropping a fifty pound charge of dynamite and blowing her to atoms."
"Dropping, you say? I understand that you cannot do otherwise than allow the bombs to fall simply by the action of gravity?"
"That is so," assented the owner of the airship. "But I think there is little possibility of their missing the mark. We took first prize at the Johannesburg Aero-Exhibition last year, placing six dummy bombs within a space eighty feet by twenty, and that from an altitude of five hundred feet."
"And your quick-firers?"
"Three-pounders."
"Not heavy enough to penetrate the plating of the 'Vorwartz,' I can assure you. Now, what do you think Karl von Harburg will be doing while you are manoeuvring to be in a position to drop one of your bombs immediately overhead?"
"I don't know," replied Captain Jones. "Why--do you?"
"Step below and I will show you a weapon that is almost identical with one carried by my rival. As you are probably aware, Karl von Harburg applied several of my inventions to his own use."
Captain Restronguet led the way below to where the aerial torpedo gun was housed.
"Here is a weapon capable of being trained fifteen degrees in any direction from a vertical," he explained. "Even when submerged to a depth of fifty feet I can discharge a projectile and hit an object a thousand feet in the air. The bursting charge throws out a shower of shrapnel with such force that no air-craft, within a radius of two hundred yards from the point of explosion, could possibly survive."
"By Jove!" ejaculated Captain Jones, his bronzed skin turning a lighter shade. "I didn't know the 'Vorwartz' carried anything like that. But no matter," he added cheerfully. "It is the fortune of war either way. I mean to do my duty in ridding the world of a pest, and if I fail it won't be for want of trying."
"Hear! hear!" exclaimed Hythe, while Captain Restronguet brought his hand down heavily upon his friendly rival's shoulder.
"That shows the British bull-dog spirit isn't dead yet," he remarked. "I am glad to hear you speak thus. You do your best: I'll do mine, and may the better man win."
The commander of the airship was shown over the "Aphrodite" and all except the essential details of her construction were minutely explained by his host. The inspection wound up with refreshments in Captain Restronguet's cabin, and in reply to an invitation Captain Restronguet, Hythe, Devoran, and Jenkins went on board the "Pride of Rhodesia." For an airship she was certainly a novelty, being built and engined in Rhodesia and of Rhodesian material--a striking testimony to the growth of one of Britain's youngest children.
Curiously enough the airship was subdivided into three compartments similar to the "Aphrodite." Thus, in the event of an accident to any two of the sections the third would be quite capable of supporting the crew and acting as a balloon; while, should the afterpart remain uninjured, it would still be able to be driven by the motors which were situated just abaft the division between the second and third sections.
"By the by, how do you combat with the deadly night airs?" asked Captain Restronguet.
"We ascend to about three thousand feet," replied the owner of the "Pride of Rhodesia." "It's a splendid climate up aloft; a guaranteed cure for all sorts of tropical fevers. How do you manage?"
"Oh, we dive," was the reply. "Our air supply is quite independent of outside atmosphere. But night is approaching, we must return."
Had there not been an element of danger should the airship attempt to combat the "Vorwartz" Captain Restronguet would have requested that Kenwyn should be temporarily accommodated on board so that the bracing air would aid his recovery, but under the circumstances he preferred to keep his second officer in the submarine.
Shaking hands Captain Restronguet and his companions bade their friendly rivals farewell and boarded their whaler. On the way back Hythe asked Jenkins what he thought of the "Pride of Rhodesia."
"Not much," replied the chief aviator to the Sultan of Zanzibar. "Not much. If I had my three-seater monoplane and a couple of hands I'd guarantee to knock spots off her as easy as kiss your hand."
"As Captain Jones said, the odds are in his favour," commented Captain Restronguet. "All the same I admire him. It will be a race for a coveted prize. Let the best man win by all means, but as sure as my name's what it is I'll do my level best to go one better than the 'Pride of Rhodesia.'"