A saying I've often heard and used "as mad as a hatter", but never knew what it meant or came from. Well today I learned during a visit to the light house on the White Cliffs of Dover. The guide explained that the light rotated on a bed of mercury, but was quite safe. Unlike hat makers, who used to work with heated mercury in their process, which used to give rise to poisonous vapours which would affect the brain and make them insane. Hence "as mad as a hatter".
Obvious when you know!
Obvious when you know!