Larklight  - Philip Reeve, David Wyatt

"How long before we can be over London?" he demanded.

McMurdo, a Scotsman [...] opined that it would take at least ten days [...].

"We shall do it in four!" declared Captain Moonfield [...]

Mr McMurdo hurried off, muttering, "I cannae do it, Captain. I'm an alchemist, not an engineer."

(show spoiler)