'Rapids!' Ramon called out. 'Rapids ahead!'
In the two and a half hours since the hovercraft's dawn departure the Rio da Morte, though flowing at a rate of about fifteen knots, had been almost glassily calm and, although visibility had been poor because of fairly heavy rain, no problems had been encountered. But now conditions had dramatically altered. At first indistinctly through the now sheeting rain, but then suddenly, frighten-ingly, and all too vividly rocks could be seen, some jagged, some curved, thrusting up from the river bed. For as far as the eye could see hundreds of them spanned the entire width of the river with white-veined, seething water coursing down between them. The hovercraft, throttled back to a point where directional control could just be maintained, was almost at once into this white and seething cauldron.
When Kellner had said that he had some little experience of navigating rapids he had been doing himself less than justice. As far as the untrained observer could see, he was masterly. He was positively dancing a jig at the controls. He no longer had the throttle pulled back but kept altering it between half and full ahead which, considering their speed, might have seemed foolhardy, but wasn't. By doing this and by ignoring the air ducts and maintaining the cushion pressure as high as possible he could all the more easily avoid making violent course alterations which would have slewed the hovercraft broadside and into disaster. Instead, he was deliberately aiming for and riding his hovercraft over the less fearsome rocks in his pat…; Even here he had to be selective, searching out the more rounded rocks and avoiding the jagged ones which, at that speed, would have ripped even the abnormally tough apron skirts, leading to the collapse of the cushion and turning the hovercraft into a boat which would then have foundered in short order. One moment he was jerking the pitch control back, putting power on the left fan, then if this proved insufficient, applying right rudder to give him directional stability while only seconds later he had to reverse the procedure. His task was made harder by the fact that even the high-speed windscreen wipers were capable only intermittently of clearing the spray and rain.
Kellner said to Hamilton who was seated beside him: 'Tell me again about all those boats that were supposed to navigate the Hoehna.'
'I guess I must have been misinformed.' Further back in the hovercraft no-one spoke because all their energies were concentrated on hanging on to their seats. The general effect of the motion was that of a roller- coaster — except that this roller-boaster, unlike the fairground type, also shook violently from side to side.
Up front, Kellner said: 'Do you see what I see?'
Some fifty yards ahead the river appeared to come to an abrupt end. They were obviously approaching a waterfall of sorts.
'Unfortunately. What are you going to do about it?'
'Funny.'
The hovercraft was being swept helplessly along to what was indeed a waterfall. The drop in the river level must have been at least ten feet. Kellner was doing the only thing he could do — trying to keep the hovercraft on a perfectly straight course.
The hovercraft swept over the fall, dipped sharply and plunged downwards at an angle of forty-five degrees. With an explosion of sound and spray, the hovercraft momentarily disappeared save for the stern. Not only the bows but part of the front of the cabin had gone completely under and in that way and at that angle the hovercraft remained for several seconds before it slowly struggled to the surface again, water cascading off its decks. It settled deeper in the water, the effect of partially losing its air cushion when the stern had come completely clear of the water.
The interior of the craft was a scene of appalling confusion. The angle of fall and the stunning impact had catapulted everyone to the deck. Equipment which had been stored but not lashed aft was now scattered throughout the cabin. To make matters worse, a window had been smashed and hundreds of gallons of water were sloshing about the interior of the cabin. One by one the passengers struggled upright. They were bruised, dazed and slightly concussed, but there seemed to be no broken bones.
As the air cushion began to fill again and the water gurgled away through the self-draining ports, they could feel the hovercraft rise slowly to its normal position.
Three times in the next few minutes the hovercraft went through a similar experience, although none of the overfalls were as high as the first time. At last the hovercraft passed into an area of smooth, rock-free water, but it was then that another danger manifested itself. The forested banks gave way to what was at first low rock, which quickly became higher and higher until they were passing through what was virtually a cliff-sided canyon. At the same time the river swiftly narrowed to about a third of its original width and the speed of the river and hence that of the hovercraft rapidly more than doubled.
Hamilton and Kellner stared through the windscreens, glanced at each other, then looked forward again. Ahead, the steep-sided river walls fell sharply away, but this promised no surcease. A quarter of a mile ahead a jumble of huge black rocks blocked the river from side to side.
'Bloouy charts!' Kellner said.
'Indeed.'
'Pity, really. These machines are very expensive.'
'Make for the left.'
'Any particular reason?'
'The Horena live on the right bank.'
'Left, as the man says.'
The rocks were about three hundred yards away. They appeared to form an impenetrable barrier, no two sufficiently far apart to afford passage to the hovercraft.
Hamilton and Kellner looked at each other. Simultaneously they shrugged. Hamilton turned and faced the rear.
'Hang on tight,' he said. 'We're about to stop very suddenly.' He had no sooner spoken than he realised that his warning had been unnecessary. They had seen what was coming up. They were already hanging on for dear life.
The rocks were now no more than a hundred yards distant. Kellner was guiding the craft towards the biggest gap between any two of them, the first and the second from the left bank.
For one brief moment it seemed that the hovercraft might just have one chance of making — the passage as Kellner arrowed straight for the centre of the gap. The craft's bows passed through but that was all: the passage was at least eighteen inches narrower than the midships beam of the hovercraft. With a grinding, screeching tearing of metal, the hovercraft came to an abrupt halt, immovably jammed.
Kellner went into reverse and applied maximum power. Nothing happened. Kellner eased off the fans but kept the engine running to maintain the cushion. He straightened up, muttering to himself, 'Now with an ocean-going tug…'
Ten minutes later there was a pile of rucksacks, canvas bags and other improvised luggage containers on deck and Hamilton was securing a rope around his waist. He said: 'It's only twenty feet to that bank but the water's mighty fast so kindly don't let go of the end of that rope.'
It was a danger, but not the only one. Even as he finished speaking there came a sudden grunt and Kellner collapsed to the deck. A dart protruded from the back of his neck. Hamilton swung round.
On the far right bank, less than fifty yards away, stood a group of Indians, ten or twelve in all. Every man had a blowpipe to his mouth.
'Horena!' Hamilton shouted. 'Down! Take cover behind the cabin, inside the cabin. Ramon! Navarro!'
Almost immediately, Ramon and Navarro, all humanitarian principles forgotten at the sight of Kellner, were on the cabin roof, stretched out on their elbows, rifles in hand. More darts struck the metal sheathing but none found a target. In three seconds the twins fired six shots. At five hundred yards either man was accurate. At fifty yards they were deadly. One after another, in those few seconds, three Horena toppled into the river, three others crumpled and died where they stood, and the others melted away.
Hamilton gazed down in bitterness at the lifeless Kellner. Not for the Horena the use of timbo, the poisonous bark of a forest vine which merely stunned: the dart which took Kellner had been tipped with curare.
Hamilton said: 'If it weren't for Kellner we'd all be dead. And now Kellner is dead.' Without another word he jumped into the river. The only danger here was the speed of the water: neither alligators nor piranha ever inhabit rapids.
At first he was swept downstream and had to be hauled back. On the second attempt he succeeded in
