In November 1941 a U-boat torpedoed the British battleship Barham, but the Germans didn’t realize they’d hit it. The British Admiralty managed to keep the loss a secret for two months, but in the interval a Scottish spiritualist named Helen Duncan announced that the Barham had sunk. She said she’d heard the news from a dead sailor.

The British authorities arrested Duncan, hoping to discredit her story. They appealed to an old law against fraudulent “spiritual” activity … which unfortunately was called the British Witchcraft Act of 1735.

So: History records that a practicing medium who revealed an “unknowable” secret at a séance in 1941 was convicted under a witchcraft law. She served 9 months.

A deaf observer of the American Civil War would have been deeply confused by the outcome of certain battles. That’s because the generals planned to hear the course of the struggle — and, in some cases, the sounds never arrived.

“Acoustic shadows” typically occur when an expected sound is absorbed somehow or deflected by windshear or a temperature gradient. In the Civil War it had significant effects at Fort Donelson, Five Forks, and Chancellorsville. At the Battle of Iuka, a north wind prevented Grant from hearing guns only a few miles away. At Perryville, Don Carlos Buell learned only from a messenger that his men were involved in a major battle.

At the Battle of Seven Pines, Joseph Johnston was 2.5 miles from the front but heard no guns. And certain sounds from the Battle of Gettysburg were inaudible 10 miles away but clearly heard in Pittsburgh.

(Thanks, David.)