The position of the "Vorwartz" was now, according to the detector, forty miles S.W. of her pursuer. When Captain Restronguet came to fix her position on the chart he knitted his brows in perplexity. The rival submarine was, if his information was correct, actually within the delta of the great Zambezi River.
"Now we have her!" exclaimed Captain Restronguet gleefully. "It will be a bit of a shock to Von Harburg when he finds that his return journey is barred by the only craft he feared and one that he thought he had destroyed."
"Do you think he's heard that the 'Aphrodite' was not smashed up after all?" asked Hythe.
"It is doubtful. If he has I can only conjecture that he has decided to ascend the Zambezi in the hope of eluding us. Otherwise I cannot suggest any reason unless he wishes to form a base in this unhealthy Portuguese territory since his Sumatran refuge is closed to him."
"I have heard that the district is reeking with fever, sir," remarked the sub. "Many times men-of-war have sent exploring parties up the river and almost invariably some, and once every man, of the crew have been stricken down. The Portuguese have, apparently, taken no active steps to rid the locality of the mosquitoes. If the deadly climate could be rendered habitable, as in the case of the Canal Zone at Panama, the Zambezi would be one of the greatest trading arteries of the world."
"Some day it will," said Captain Restronguet. "The British Government has had its eye upon Portuguese East Africa for some time. Could the Portuguese Republic be induced to sell it there would be a splendid outlet for Rhodesia, and under active management the Zambezi would make a splendid waterway. Even now it is navigable as far as Kebrabassa Falls, nearly three hundred miles from the delta."
"It strikes me, sir, that we shall be grilling in a fetid atmosphere before many hours are past," observed Devoran. "Why couldn't Karl von Harburg stick to the sea?"
"There's nothing like variety," replied Captain Restronguet complacently. "After we've settled with the 'Vorwartz' we may have a little shooting; lions and rhinos are fairly plentiful, to say nothing of smaller fry. But I do not think we need entertain fears of the climate. It is only at night that the pestilential mists are really dangerous. Every day just before sunset, we will submerge the 'Aphrodite,' since there is reason to suppose there are deep holes in the bed of the river for this to be done even if the normal depth is insufficient. We shall not thus be inhaling the noxious gases, nor be exposed to the attacks of mosquitoes and other germ-bearing insects; whilst river-water passed through our condensers will be perfectly drinkable."
According to the rosy views held by the captain of the "Aphrodite" the new phase of the cruise was to be a sort of picnic; but he had reckoned without his host.
On arriving off the First Bluff Point, on the western side of the main outlet of the Zambezi, it was found that there was such a heavy tumble on the bar that to attempt to cross it would be an impossible task.