Execution during the Civil War took different forms for combatants and civilians. Combatants—soldiers wearing their uniforms—who engaged in spying or sabotage, were entitled to be executed by firing squad, whereas civilians were hanged. Hanging was considered a dishonorable way to die.
"Peyton Farquhar was dead; his body, with a broken neck, swung gently from side to side beneath the timbers of the Owl Creek bridge..."See in text(III)
This ending--horrible and surprising--is characteristic of Ambrose Bierce's short stories, particularly his Civil War stories, which all end with an ironic twist that often surprises the reader because of the matter-of-fact tone Bierce uses to describe a horrific scene.
These are harps that make music when wind passes over the strings. Originating in the ancient world, they are named after Aeolus, the Greek god of the wind.
This refers to Niagara Falls, the common name for three waterfalls located at the international border between Ontario, Canada, and the state of New York.