“On your feet, Rillomyner,” he called out. “It’s time you started earning your pay on this trip.”

The mechanic stood up and came out of the passenger compartment. “I’m sorry, captain — the way we took off did something to my gut.”

“Get on to the cannon if you don’t want to be really sick,” Toller said. “We might be having a visitor soon.”

Rillomyner swore and lurched towards the nearest cannon. Zavotle and Flenn followed suit without needing to be ordered. There were two of the anti-ptertha guns mounted on each side of the gondola, their barrels made of thin strips of brakka bonded into tubes by glass cords and resin. Below each weapon was a magazine containing glass power capsules and a supply of the latest type of projectile — hinged bundles of wooden rods which opened radially in flight. They demanded better accuracy than the older scattering weapons, but compensated with improved range.

Toller remained at the pilot’s station and fired intermittent bursts of heat into the balloon to maintain the rate of climb. He was not unduly concerned about the lone ptertha and had issued his warning as much to rouse Rillomyner as anything else. As far as was known, the globes depended on air currents to transport them over long distances, and only moved horizontally of their own volition when close to their prey. How they obtained impulsion over the final few yards was still a mystery, but one theory was that a ptertha had already begun the process of self-destruction at that stage by creating a small orifice in its surface at the point most distant from the victim. Expulsion of internal gases would propel the globe to within the killing radius before the entire structure disintegrated and released its charge of toxic dust. The process remained a matter for conjecture because of the impossibility of studying ptertha at close range.

In the present case the globe was about four-hundred yards from the ship and was likely to stay at that distance because the positions of both were governed by the same air-flow. Toller knew, however, that the one component of their motion over which the ptertha had good control was in the vertical dimension. Observation through calibrated telescopes showed that a ptertha could govern its attitude by increasing or decreasing its size, thus altering its density, and Toller was interested in carrying out a double experiment which might be of value to the migration fleet.

“Keep your eye on the globe,” he said to Zavotle. “It seems to be keeping on a level with us, and if it is that proves it can sense our presence over that distance. I also want to find out how high it will go before giving up.”

“Very good, captain.” Zavotle raised his binoculars and settled down to studying the ptertha.

Toller glanced around his circumscribed domain, trying to imagine how much more cramped its dimensions would seem with a full complement of twenty people on board. The passenger accommodation consisted of two narrow compartments, at opposite sides of the gondola for balance, bounded by chest-high partitions. Nine or so people would be crammed into each, unable either to lie down properly or move around, and by the end of the long voyage their physical condition was likely to be poor.

One corner of the gondola was taken up by the galley, and the diagonally opposite one by the primitive toilet, which was basically a hole in the floor plus some sanitation aids. The centre of the floor was occupied by the four crew stations surrounding the burner unit and the downward facing drive jet. Most of the remaining space was filled by the pikon and halvell magazines, which were also at opposite sides of the gondola, with the food and drink stores and various equipment lockers.

Toller could foresee the interplanetary crossing, like so many other historic and glorious adventures, being conducted in squalor and degradation, becoming a test of physical and mental endurance which not all would survive.

In contrast to the meanness and compression of the gondola, the upper element of the skyship was awesomely spacious, rarified, a giant form almost without substance. The linen panels of the envelope had been dyed dark brown to absorb the sun’s heat and thereby gain extra lift, but when Toller looked up into it through the open mouth he could see light glowing through the material. The seams and horizontal and vertical load tapes appeared as a geometric web of black lines, emphasising the vastness of the balloon’s curvatures. Up there was the gossamer dome of a cloud-borne cathedral, impossible to associate with the handiwork of mere weavers and stitchers.

Satisfied that the ship was stable and ascending steadily, Toller gave the order for the four acceleration struts to be drawn in and attached by their lower ends to the corners of the gondola. Renn completed the task within a few minutes, imparting to the balloon/gondola assemblage the slight degree of structural stiffness needed to cope with the modest forces which would act on it when the drive or attitude jets were in use.

Attached to a lashing hook at the pilot’s station was the rip line, dyed red, which ran up through the balloon to a crown panel which could be torn out for rapid deflation. As well as being a safety device it served as a rudimentary climb speed indicator, becoming slack when the crown was depressed by a strong vertical air flow. Toller fingered the line and estimated that they were ascending at about twelve miles an hour, aided by the fact that the miglign gas was slightly lighter than air even when unheated. Later he would almost double that speed by using the drive jet when the ship entered the regions of low gravity and attenuated air.

Thirty minutes into the flight the ship was high above the summit of Mount Opelmer and had ceased its eastward drift. The garden province of Kail stretched to the southern horizon, its strip farms registering as a shimmering mosaic, with each tessera striated in six different shades varying from yellow to green. To the west was the Otollan Sea and to the east was the Mirlgiver Ocean, their curving blue reaches flecked here and there by sailing ships. The ochraceous mountains of Upper Kolcorron filled the view to the north, their ranges and folds compacted by perspective. A few airships gleamed like tiny elliptical jewels as they plied the trade lanes far below.

From an altitude of some six miles the face of Land looked placid and achingly beautiful. Only the relative scarcity of airships and sailing craft indicated that the entire prospect, apparently drowsing in benign sunlight, was actually a battle-ground, an arena in which mankind had fought and lost a deadly duel.

Toller, as had become his habit when deep in thought, located the curiously massive object given to him by his father and rubbed his thumb over its gleaming surface. In the normal course of history, he wondered, how many centuries would men have waited before essaying the voyage to Overland? Indeed, would they ever have done so had they not been fleeing from the ptertha?

The thought of the ancient and implacable enemy prompted him to cast around and check on the position of the solitary globe he had detected earlier. Its lateral separation from the ship had not changed and, more significantly, it was still matching the rate of climb. Was that proof of sentience and purpose? If so, why had the ptertha as a species singled out man as the focus of its hostility? Why was it that every other creature on Land, with the exception of the Sorka gibbon, was immune to pterthacosis?

As though sensing Toller’s renewed interest in the globe, Zavotle lowered his binoculars and said, “Does it look bigger to you, captain?”

Toller picked up his own glasses and studied the purple-black smudge, finding that its transparency defied his attempts to define its boundaries. “Hard to say.”

“Littlenight will be here soon,” Zavotle commented. “I don’t relish the idea of having that thing hanging around us in the dark.”