Then Deryn saw the knot over her head - the cable that bound the airbeast to the ground!
She looked at the cable stretched out between her and the winch ... about three hundred feet of it now. That length of rain-soaked hemp had to weigh more than one skinny wee lassie and her wet clothes.
If she could set the Huxley free, it might still have enough hydrogen to carry her up to safety.
But the ground was rising again, shining wet grass and puddles blurring past just beneath her feet - the prison walls ahead. Reaching up with one hand, Deryn felt the half-familiar shape of the knot... .
It was nothing but a backhanded mooring hitch! She remembered Jaspert telling her how Air Service riggers used sailor's knots, the same ones she'd tied a thousand times on Da's balloons!
As Deryn struggled to free the wet cable from its knot, her boots struck the ground with a bone-jarring thud, skidding across the wet grass.
But the real danger wasn't below - it was the approaching prison walls. Deryn and the Huxley were seconds away from smashing into that shining expanse of wet stone.
Finally her fingers pushed the cable's working end free. The knot spilled, the rope twisting like a live thing, skinning her fingers as it slipped from the steel ring.
As the weight of three hundred feet of wet hemp dropped away, the airbeast soared, clearing the prison walls with yards to spare.
Deryn's breath caught as a belching chimney passed beneath her feet. She imagined raindrops tumbling down its mouth to the coal fires below, spitting steam, the sparks rising up to ignite the angry mass of hydrogen over her head.
But the wind whipped the sparks away - moments later the Huxley had cleared the southernmost prison buildings.
As she climbed, Deryn heard a hoarse cheer from below.
The ground men raised their arms in triumph. Jaspert was beaming, cupping both hands to his face and shouting something that sounded congratulatory, as if to say she'd done exactly what he'd told her!
"It was my barking idea, Jaspert Sharp," she muttered, sucking her rope-burned fingers.
Of course, she was still in the middle of a storm, strapped to an irritable Huxley, both of them soaring across a stretch of London with precious few spots to land.
And how was Deryn meant to land this beastie? She had no way to vent hydrogen, no more ballast in case the creature spooked, and no clue if anyone had ever free-ballooned with a Huxley before and lived to tell the tale.
Still ... at least she was flying. If she ever came down alive, the boffins would have to admit as how she'd passed this test.
Boy or not, Deryn Sharp had shown a squick of air sense after all.
EIGHT
The storm felt strangely still.
She remembered the sensation from Da's hot-air balloons. Cut free from its tether, the medusa had exactly matched the speed of the wind. The air felt motionless, the earth turning below on a giant lathe.
Dark clouds still boiled around her, giving the Huxley an occasional spin. But worse were the flickers in the distance. One sure way to set a hydrogen breather aflame was to hit it with lightning. Deryn distracted herself by watching London pass beneath, all matchbox houses and winding streets, the factories with their sealed smokestacks.
She remembered how Da had said London looked in the days before old Darwin had worked his magic. A pall of coal smoke had covered the entire city, along with a fog so thick that streetlamps were lit during the day. During the worst of the steam age so much soot and ash had decorated the nearby countryside that butterflies had evolved black splotches on their wings for camouflage.
But before Deryn had been born, the great coal-fired engines had been overtaken by fabricated beasties, muscles and sinews replacing boilers and gears. These days the only chimney smoke came from ovens, not huge factories, and the storm had cleared even that murk from the air.
Deryn could see fabs wherever she looked. Over Buckingham Palace a flock of strafing hawks patrolled in spirals, carrying nets that would slice the wings off any aeroplane that ventured too close. Messenger terns crisscrossed the Square Mile, undeterred by the weather. The streets were full of draft animals: hippoesques and equine breeds, an elephantine dragging a sledge full of bricks through the rain. The storm that had almost snuffed out her Huxley had barely slowed the city down.
Deryn wished she had her sketch pad, to capture the tangle of streets and beasts and buildings below. She'd first started drawing up in one of Da's balloons, trying to capture the wonders of flight.
As the clouds gradually broke apart, the Huxley slid across a shaft of light. Deryn stretched in the warmth, and set to squelching water out of her cold, damp clothes.
The houses below were getting smaller, the teeming umbrella tops blurring into the wet streets. As it dried, the Huxley was climbing.
Deryn frowned. To descend in a balloon, you vented hot air from the top. But Huxleys were primitive ascenders, designed to be tethered at all times.
What was she supposed to do, talk the beastie down?
"Oi!" she shouted. "You there!"
The nearest tentacle curled a bit, but that was all.
"Beastie! I'm talking to you!"
No reaction.
Deryn scowled. An hour ago the Huxley had been so easy to spook! Perhaps one annoyed lassie's cries didn't amount to much after the terrific storm.
"You're a big, bloated bum-rag!" she shouted, swinging her feet to rock the pilot's rig. "And I'm getting bored of your company! Let! Me! Down!"
The tentacles uncurled, like a cat stretching in the sun.
"That's just brilliant," she grumbled. "I'll add rudeness to your defects."
Passing through another patch of sun, the medusa made a soft sighing noise, expanding its airbag to dry itself.
Deryn felt herself drifting higher.
She groaned, looking at the blue skies ahead. She could see all the way to the farmlands of Surrey now. And past that would be the English Channel.
For two long years Deryn had wanted nothing more than to go aloft again, like when Da had been alive - and here she was, marooned in the sky. Maybe this was punishment for acting like a boy, just like her mum had always warned.
The wind steadied, pushing the beast toward France.
It was going to be a long day.
The Huxley noticed it first.
The pilot's rig jolted under Deryn, like a carriage going over a pothole. Shaken from a catnap, she glared up at the Huxley.
"Getting bored?"
The airbeast seemed to be glowing, the sun shining straight down through iridescent skin. It was noon, so she'd been aloft more than six hours. The English Channel sparkled not far ahead, set against a perfect sky. They'd left London's gray clouds far behind.