London

"Oh no," Dr. Childermass said. "Mag-Lev is just a shorter way of saying Mag-netic Levitation."

"It floats!" said Wolf, gazing down at the new city entranced. "Like a gigantic hovercraft...."

Dr. Childermass gave him a graceful nod, pleased that at least one of her listeners was keeping up. "Rather quieter than a hovercraft, Herr Kobold, and not nearly so hungry for fuel. More like a very large, low-flying airship. You see those silvery disks along the flanks and underbelly?"

Tom, Wren, and Wolf nodded in unison. There was no missing the disks, dirty metal mirrors fifty feet across, swivel-mounted like an airship's engine pods.

"Those are what I call Magnetic Repellers. Once they are powered, the whole city will be able to swim in the currents of the earth's magnetic field. It will hang a few feet abovethe ground--or above the water; indeed, it makes no difference. The small prototypes we made worked splendidly. All we need do now is to complete the electromagnetic engine that powers the repellers--"

Chapter 23, The Childermass experiment, a Darkling Plain

THE LONDONERS HAD ALWAYS imagined themselves leaving the debris  fields in a leisurely way, perhaps moving at no more than walking speed until they  grew used to New London's controls. Instead, here they were, barreling north  through the wreck of old London as fast as the new city could go, slaloming  around tumbles of old tier supports and giant, corroded heaps of tracks and  wheels. Down in the engine rooms the Engineers heaved desperately on the levers  that angled the Magnetic Repellers, while up in the steering chamber at the top of  the town hall Mr. Garamond and his navigators peered out through unglazed,  unfinished viewing windows and shouted to the helmsmen, "Left a bit! Right a bit!  Right a bit! Oh, I mean, left, left, LEFT!"

Chapter 51: The Chase, A darkling Plain