By the third day of the ascent the sky, although retaining its normal coloration above and below, was shading on all sides of the ship into a deeper blue which glistered with ever-increasing numbers of stars.

When Toller was lost in his tranced vigils the conversation of the crew members and even the roar of the burner faded from his consciousness, and he was alone in the universe, sole possessor of all its scintillant hoards. Once during the hours of darkness, while he was standing at the pilot’s station, he saw a meteor strike across the sky below the ship. It traced a line of fire from what seemed to be one edge of infinity to the other, and minutes after its passing there came a single pulse of low-frequency sound — blurred, dull and mournful — causing the ship to give a tentative heave which drew a murmur of protest from one of the sleeping men. Some instinct, a kind of spiritual acquisitiveness, prompted Toller to keep the knowledge of the event from the others.

As the ascent continued Zavotle was kept busy with his copious flight records, many of the entries concerned with physiological effects. Even at the summit of the highest mountain on Land there was no discernible drop in air pressure, but on previous high-altitude sorties by balloon some crew members had reported a hint of thinness to the air and the need to breathe more deeply. The effect had been slight and the best scientific estimate was that the atmosphere would continue to support life midway between the two planets, but it was vital that the predication should be verified.

Toller was almost comforted by the feel of his lungs working harder during the third day — more evidence that the problems of interworld flight had been correctly foreseen — and he was therefore less than happy when an unexpected phenomenon forced itself on his attention. For some time he had been aware of feeling cold, but had dismissed the matter from his thoughts. Now, however, the others in the gondola were complaining almost continuously and the conclusion was inescapable — as the ship gained altitude the surrounding air was growing colder.

The S.E.S. scientists, Lain Maraquine included, had been of the opinion that there would be an increase in temperature as the ship entered ratified air which would be less able to screen it from the sun’s rays. As a native of equatorial Kolcorron, Toller had never experienced really severe coldness, and he had thought nothing of setting off on the interplanetary voyage clad in only a shirt, breeches and sleeveless jupon. Now, although not actually shivering, he was continuously aware of the increasing discomfort and a dismaying thought was beginning to lurk in his mind — that the entire flight might have to be abandoned for the lack of a bale of wool.

He gave permission for the crew to wear all their spare clothing under their uniforms, and for Flenn to brew tea on demand. The latter decision, far from improving the situation, led to a series of arguments. Time after time Rillomyner insisted that Flenn, acting out of malice or ineptitude, was either infusing the tea before the water had boiled properly or was allowing it to cool before serving it around. It was only when Zavotle, who had also been dissatisfied, kept a critical eye on the brewing process that the truth emerged — the water had begun to boil before it had reached the appropriate temperature. It was hot, but not “boiling” hot.

“I’m worried about this finding, captain,” Zavotle said as he completed the relevant entry in the log. “The only explanation I can think of is that as the water gets lighter it boils at a progressively lower temperature. And if that is the case, what is going to happen to us when the weight of everything fades away to nothing? Is the spit going to boil in our mouths? Are we going to piss steam?”

“We would be obliged to turn back before you had to suffer that indignity,” Toller said, showing his displeasure at the other man’s negative attitude, “but I don’t think it will come to that. There must be some other reason — perhaps something to do with the air.”

Zavotle looked dubious. “I don’t see how air could affect water.”

“Neither do I — so I’m not wasting time on useless speculation,” Toller said curtly. “If you want something to occupy your mind take a close look at the height gauge. It says we’re eleven-hundred miles up — and if that is correct we have been seriously underestimating our speed all day.”

Zavotle studied the gauge, fingered the rip line and looked up into the balloon, the interior of which was growing dim and mysterious with the onset of dusk. “Now that could be something to do with the air,” he said. “I think that what you have discovered is that thinner air would depress the crown of the envelope less at speed and make it seem that we’re going slower than we actually are.”

Toller considered the proposition and smiled. “You worked that out — and I didn’t — so give yourself credit for it in the record. I’d say you’re going to be the senior pilot on your next flight.”

“Thanks, captain,” Zavotle said, looking gratified.

“It’s no more than you deserve.” Toller touched Zavotle on the shoulder, making tacit reparation for his irritability. “At this rate we’ll have passed the thirteen-hundred mark by dawn — then we can take a rest from the burner and see how the ship handles on the jet.”

Later, while he was settling down on the sandbags to sleep, he went over the exchange in his mind and identified the true cause of the ill temper he had vented on Zavotle. It had been the accumulation of unforeseen phenomena — the increasing coldness, the odd behaviour of the water, the misleading indication of the balloon’s speed. It had been the growing realisation that he had placed too much faith in the predictions of scientists. Lain, in particular, had been proved wrong in three different respects, and if his vaulting intellect had been defeated so soon — on the very edge of the region of strangeness — nobody could know what lay in store for those setting out along the perilous fractured glass bridge to another world.

Until that moment, Toller discovered, he had been naively optimistic about the future, convinced that the proving flight would lead to a successful migration and the foundation of a colony in which those he cared about would lead lives of endless fulfilment. It was chastening to realise that the vision had been largely based on his own egotism, that fate had no obligation to honour the safe conducts he had assigned to people like Lain and Gesalla, that events could come to pass regardless of his considering them unthinkable.

All at once the future had clouded over with uncertainty and danger.

And in the new order of things, Toller thought as he drifted into sleep, one had to learn to interpret a new kind of portent. Day-to-day trivia… the degree of slackness in a cord… bubbles in a pot of water… These were niggardly omens… whispered warnings, almost too faint to hear.… By morning the height gauge was showing an altitude of fourteen-hundred miles, and its supplementary scale indicated that gravity was now less than a quarter of normal.

Toller, intrigued by the lightness of his body, tested the conditions by jumping, but it was an experiment he tried only once. He rose much higher than he had intended and for a moment as he seemed to hang in the air there was a terrible feeling of having parted from the ship for ever. The open gondola, with its chest-high walls, was revealed as a flimsy edifice whose pared-down struts and wicker panels were quite inadequate for their purpose. He had time to visualise what would happen if a floor section gave way when he landed on it, plunging him into the thin blue air fourteen-hundred miles above the surface of the world.

It would take a long time to fall that distance, fully conscious, with nothing to do but watch the planet unfurl hungrily below him. Even the bravest man would eventually have to begin screaming.…