Frigate shook himself like a dog coming out of water, and he got down to the work that keeps a balloon pilot busy during much of the flight. He checked the altimeter. One thousand eight hundred and twenty-nine meters. A little over 6000 feet. The verimeter, or statoscope, indicated that the rate of ascent was increasing as the sun warmed the gas in the bag. After checking the O and H storage chambers were full, he disengaged the battery from the water. For the present, he had nothing to do except keep an eye on the altimeter and verimeter.

The Valley narrowed. The blue-black mountains, splotched with vast patches of grey-green and blue-green lichen, sank. The mists that ribboned the stream and the plains were disappearing as swiftly as mice that had gotten word a cat was in the neighborhood.

They were being carried southward increasingly swifter. "We're losing ground," Frisco muttered. However, he spoke only to re­lease nervous tension. Test balloons had shown that the stratosphe­ric wind would carry them northeast.

Frigate said, "Last chance for a cigarette." Everybody except Nur lit up. Though smoking had been forbidden on all hydrogen balloons previous to the Jules Verne, it was permitted on it at lower altitudes. There was no sense in worrying about burning tobacco while an operating torch was present.

Now the balloon had risen above the Valley, and they thrilled at the sight of more than one at a time. There they were, row on row. To their left were the valleys-broad, deep canyons actually- which they had passed in the Razzle Dazzle. And as they soared higher, the horizon rushed outward as if in a panic. Frigate and Rider had seen this phenomenon on Earth, but the others gazed in awe. Pogaas said something in Swazi. Nur murmured, "It's as if God were spreading out the world like a tablecloth."

Frigate had all the ports closed, and he turned on the oxygen supply and a little fan which sucked carbon dioxide into an absor­bent material. At 16 kilometers or almost 10 miles altitude, the Jules Verne entered the tropopause, the boundary between troposphere and stratosphere. The temperature outside the cabin was - 73 C.

Now the contrary wind seized the aerostat and in so doing slightly spun it. From then on, unless they encountered an opposing wind, they would have the view of a rider on a lazy merry-go-round.

Nur took over the pilot's post. Pogaas got the next, and Rider had the third watch. When Farrington became the pilot, he lost his nervousness. He was in control, and that made all the difference. Frigate was reminded of how Farrington had described in a book his fierce exultation when, at the age of seventeen, he'd been allowed to steer a sealing schooner in rough weather. After watching him for a few minutes at the wheel, the captain had gone below. Farrington was the only one above decks, the safety of the ship and its crew in his hands. It had been an ecstatic experience never surpassed in a life filled with perilous adventures.

However, as soon as Frigate relieved him, he lost his smile, and he looked as uneasy as before.

The sun continued to rise and with it the Jules Verne. The envelope was near its pressure height now, which meant that the joy ride was over. Since its neck was sealed, instead of being open as in most manned aerostats, it would keep rising until overexpanded. At this point the bag would rupture, and down would come everybody posthaste with a postmortem afterward. But provisions had been made for this.

Frigate checked the altimeter and then rotated a metal drum set in the overhead. This was attached by a rope to a wooden valve in the neck of the bag. It opened, releasing some gas. The balloon sank. It would shortly begin rising again, though, which meant more gas would have to be valved off. This called for operation of the torch at intervals, and also for shutting off the torch and feeding hydrogen into the balloon.

It required cool and accurate judgment to know just how much gas to valve and how much to replace. Too much valved off meant a too fast fall. Too much new gas meant that the craft could ascend beyond the pressure height. A safety valve on top of the bag would automatically release gas to prevent bursting of the bag-if the valve hadn't frozen-but the balloon would then become, possibly, too heavy.

In addition, the pilot had to watch out for unexpectedly warm layers of air. These could lift the Jules Verne too swiftly and carry it above the pressure height. A sudden cooling off could precipitate the craft downward.

The pilot could in the latter situation order ballast thrown out, but this might result in a yoyo morion. And if he lost all his ballast, he was in trouble. The only way to lose altitude quickly was to release more gas. Which meant that the burner might not be able to expand the hydrogen quickly enough.

Nobody Knows the Troubles I've Seen would be his swansong. However, the day passed without any nerve-wracking emergen­cies. The sun sank, and the Jules Verne, its hydrogen cooling, did likewise. The pilot had to run the burner just enough to raise it now and then and keep the vessel above the tropopause. Those off-duty snuggled under heavy cloths and slept according to their natures. Being the only one awake at night was eerie. The illumination was feeble. The starlight poured into the ports, but this, with some small lights above the gauges and dials, was not enough for com­fort. The alloy hull amplified every noise: the impact of a hand on the deck as somebody turned over and flung out an arm; Pogaas muttering Swazi; Frisco grinding his teeth; Rider softly whinnying horselike; the fan whirring.

When Frigate ignited the torch, the sudden explosion and suc­ceeding roar startled everybody from sleep. Then it was his turn to burrow under the cloths, to sleep, to be roused momentarily by the torch or a nightmare of falling.

Dawn came. The crewmen got up at different times, used the chemical toilet, drank hot instant coffee or tea, and ate food saved from the grails, supplemented by acorn bread and dried fish. The wastes from the toilet were not jettisoned. Opening a hatch at this altitude meant a possibly fatal drop in air pressure, and any weight loss increased the lift.

The Frisco Kid, whose eye was best at estimating ground speed, though they were clipping along at 50 knots.

Before noon, the vessel was gripped by a wind that took them backward for several hours before it curved the craft around north­east again. After three hours they were going southward again.

"If this keeps up we'll whirl around here forever," Frigate said gloomily. "I don't understand this."

Late that afternoon they were back on the proper course. Frigate said that they should descend to the surface winds and try their luck there. They were far enough north to be where the winds generally flowed toward the northeast.

By letting the burner stay off, the gas slowly cooled. The Jules Verne sank at a minuscule rate at first, then began dropping swiftly. Nur turned the burner on for a few minutes to check its descent. At 13 kilometers altitude, the wind lessened. It picked up again and in an opposite direction, the wrong one for them. It also gave the craft a counterspin. Nur allowed it to sink until it was about 2000 meters above the mountaintops. Now they moved at an angle across the valleys, which were running straight north and south in this area.

"We're going northeast again!" Frigate said happily.

At high noon of the third day they were sailing along at an estimated 25 kmph or more than 15 mph. Only the Jules Verne could have gotten this far. Any other type of balloon would not have been able to ascend to the stratosphere or descend to the surface winds without losing too much gas to go on.

They opened the ports to let the thin but fresh air in. The up- and downdrafts caused them some discomfort, chiefly from the change in air pressure. They had to keep swallowing and yawning to ease their eardrums. As dusk approached, the drafts became less vio­lent.