A gas-powered flare aides a police officer directing traffic in the London fog. "The device can be folded up and put in a metal box sunk in the street," read The Times caption for this photo on October 23, 1935. Somehow, these failed to catch on.
London's infamous fog dates back to the 1800s and pollution from the Industrial Revolution. "The British capital is particularly liable to natural winter fog," Christine L. Corton wrote for The Times in 2015. "It is surrounded by low hills, with marshland on its outskirts, and a large river running through it. Its location encourages the meteorological phenomenon of temperature inversion, when warm air traps cold air beneath it for days on end.
"During such a fog, the sulfur-laden smoke from domestic coal fires and factory chimneys was unable to rise into the upper atmosphere, and seeped into the natural fog, turning it yellow, brown, green or black - a process beautifully captured by Claude Monet in his series of paintings of London fog.
"Such fogs were known as 'pea soupers.' As the name suggested, they were often so thick that people could not see their own feet as they walked through them on the city streets. As the city grew, these fogs occurred more frequently; they became more dense, and they lasted longer."
