Concave sails focused distant bell sound onto a ship 100 miles away

Evidence

It happened once, on board a ship, sailing along the coast of Brazil, 100 miles from land, that the persons walking on deck, when passing a certain spot, heard most distinctly the sound of bells varying as in human rejoicing. All on board listened and were convinced, but the phenomenon was mysterious and inexplicable. Some months afterwards it was ascertained that the bells of the city of St. Salvador, on the Brazilian coast, had been ringing that very day on the occasion of a festival. The sound had, therefore, travelled over 100 miles of smooth water, and, striking the wide-spread sails of the ship, rendered concave by the breeze, had been brought to a focus, and rendered perceptible to all on board. — Eric J. Heller, Why You Hear What You Hear- An…, 127

Categorization

• CANDY: A 100-mile sound focus by concave sails is a delightful, self-contained conversation piece about acoustics.
• XREF: Relates to how curved surfaces (like parabolic reflectors) focus sound waves — connects to acoustic mirror defenses and whispering galleries.