the poster that this incredible illustration is based on is extremely striking. but while searching for it, I also found earlier posters for conveying this message along with a corresponding one for summer, and I fucking love them. absolutely lovely graphic design work. (both are from 1924, artist is Austin Cooper)
the one I was looking for originally also has a summer variant. (artist is Frederick Charles Herrick: 'it is warmer below' is from 1927, 'it is cooler below' is 1926)
I love these posters. Do you know what I also love? Every Londoner who's ever taken the Underground in a heatwave* in the notes currently yelling “‘it's cooler below’ MY ARSE”.
(*or in summer, or even when it's just mildly sunny outside)
But it was cooler down below in the 1920s when the posters were made!
Back then the clay of the tunnels was consistently about 14/15°C year round so warmer than winter temps and cooler than summer.
The underground running through them for years has heated the clay up and it stores heat which now can't dissipate so the base temperature of the clay is much much higher and it radiates the heat to the tunnels etc
