National Geographic : 1941 Apr
Everyday Life in Wartime England 503 London Office Workers Depend on Their Own Roof-top Plane Spotters When general air raid alarms sound during business hours, many employees no longer speed to shelters, but grab binoculars and rush to the roofs to see which way the raiders are flying. Usually the spotters cannot see the high-flying planes, but trace their course by the white puffs of smoke from exploding anti aircraft shells. If the raiders are flying away, or at an angle, the spotters give no signal. Should the white puffs show the planes approaching on a line with the building, then office forces are warned. Photographs from Acme Babies Sleep in Hammocks Slung Between the Rails in Aldwych Underground Station Some tracks, below the level of the Thames, lead into tubes beneath the river. Because a direct underwater hit by a bomb on these tubes could submerge an entire station, huge floodgates, which can be closed instantly, have been built at tunnel entrances.