However, this current itself twists around and around as it flows through the magnetic field, the way a torrent of water twists up a fire-fighter's hosepipe.

ECONOMIST: Here be serpents

"Local employers have an equally important role to play in the success of the retained fire-fighter system by allowing their employees to become retained firefighters, " he added.

BBC: NI fire service recruiting part-time firefighters

McCain, who survived two plane crashes and a massive fire aboard the USS Forrestal before his A-4 Skyhawk fighter-bomber was shot down over Hanoi in 1967, said he had not given much thought to the possibility of threats to his life as a high-profile presidential candidate.

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The aircraft maintains the air-to-air combat ability of the main F-15 fighter as the pilot can detect and fire at other aircraft.

BBC: News | In Depth | Military Fact Files