Flavio Gioja

Statute of Flavio Gioja in Amalfi by Alfonso Balzico, 1900

Flavio Gioja or Gioia (c. 1300) was reputed to be an Italian mariner and inventor, supposedly a marine pilot, and has traditionally been credited with perfecting the sailor's compass by suspending its needle over a fleur-de-lis design, which pointed North, also enclosing the needle in a little box with a glass cover.

Gioia was also said to have introduced the fleur-de-lis design in deference to Charles of Anjou, the French king of Naples.)

Flavio Gioia's birthplace is alternately given as Amalfi, Positano, Naples, and, Gioia, a town in Apulia, hence the derivation of the reputed surname.

The historical misunderstanding may be the result of a simple error in syntax: the Italian historian Flavio Biondo wrote that the compass was invented by Amalfitans. This attribution was then passed on as a Flavio dicitur, i.e. "to Amalfitans, as reported by Flavio". An interposition of a comma by mistake would then read a Flavio, dicutur, changing the meaning to "to the Amalfitan, Flavio, so they say." Later, Lilio Gregorio Giraldi attributes (in his De Re Nautica from 1540) the invention of the compass to this "Flavio of Amalfi." A later historian, Scipione Mazzella, a Neapolitan, claimed (about the year 1600) that Flavio was from Gioia, a town in Apulia, explaining his use of the name Gioia.

The lunar crater Gioja is named after him.

Sources

• Si trattò soltanto di un errore dovuto ad una virgola (It was just a mistake caused by a comma) (found at sapere.it, stored at archive.org)