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 a.s.sociated 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 const.i.tuted 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, spa.r.s.ely-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.

"Pa.s.s 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 a.s.sent and soon the airship was riding head to wind with her nacelles just resting on the water.

Hythe hurriedly explained the circ.u.mstances 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," a.s.sented 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 s.p.a.ce eighty feet by twenty, and that from an alt.i.tude of five hundred feet."

"And your quick-firers?"

"Three-pounders."

"Not heavy enough to penetrate the plating of the 'Vorwartz,' I can a.s.sure 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!" e.j.a.c.u.l.a.t.ed 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 circ.u.mstances 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.'"