"Ah, that is what we want," remarked Captain Restronguet, pointing to a ship's whaler lying on the quay. "Under the circumstances, considering how extortionately we have been charged, I have no qualms in annexing yon craft."
The whaler was a heavy one, but a dozen men soon brought her on board. This done the "Aphrodite" cautiously made her way upstream, for mudbanks and shoals abounded, and only by the frequent use of the lead was the submarine, running light, able to keep to the main channel.
It was now within two hours of sunset, and the "Aphrodite" had to find a suitable berth in order to carry out the plans Captain Restronguet had suggested for the safeguarding of his crew.
The confiscated boat had been securely lashed down amidships. It was too large to be taken below through the hatchway, but in order that it would not burst its lashings as the submarine sank Mylor bored four fairly large holes in the garboards so that the water could easily make its way out. The holes could be plugged when the whaler was required for service afloat, and as Hythe remarked an additional washing would do a lot of good to a boat that had been left lying on the wharf of that malodorous and inhospitable town.
Fortunately a fairly deep and extensive hole was discovered in the bed of the river, the soundings giving ten fathoms. Being the rainy season the river was three or four feet higher than its normal level, a circumstance greatly in the favour of the submarine's voyage of exploration and retribution.
The night passed fairly quietly, the air within the submarine being perfectly clear. Looking through the observation scuttle the crew could see that the so-called fresh water was of a deep brown colour, while the full moon, shining through the miasmic mists looked like a ball of greenish yellow copper. Occasionally a crocodile would alight upon the deck of the "Aphrodite" and drag its armoured body over the metal plating with a dull metallic sound. Once a couple of hippopotami in their moonlight gambols brushed against the side of the conning-tower, the shock being distinctly felt by the men on watch.
In the morning the detector registered the position of the "Vorwartz" at eighty-five miles, which was precisely the same distance as it gave overnight.
Not until the mists had disappeared did Captain Restronguet order the "Aphrodite" to be brought to the surface and the hatchways opened. He would not risk the health of his crew by exposing them to the fever-laden atmosphere. Almost as far as the eye could reach the water extended, for being in flood the river, wide under ordinary circumstances, now resembled a vast lake.
Proceeding at twelve knots, that took her over the ground against the current at barely nine miles an hour, the submarine held steadily on her course, literally feeling her way between the shoals of loathsome black mud.
Just before noon a motor-launch manned by Portuguese passed, downward bound. In reply to a signal to close, the little craft ran alongside the "Aphrodite" without the faintest hesitation. Two of her crew who could speak French were interrogated by Hythe. They had neither seen nor heard anything of a vessel resembling the "Vorwartz" although they had come from Tete, a few miles below the limit for navigation. In reply to a request that one of their number should accompany the submarine as far as Sena, to act as a pilot, the Portuguese resolutely refused, saying that a qualified man could be obtained at Molonho, ten miles further up the river.