Poseidon's Trident, and Salacia at His Side

Once merged with Poseidon, Neptune took on the Greek god's trident, his stormy temper, and his myths, becoming the bearded ruler of the deep who raises and stills the waves. The Romans paired him with an old Italian water-goddess, Salacia, understood as the personification of the surging salt sea, and sometimes with Venilia as well. As Rome became a naval and maritime power, the sea-god grew in public importance, and Neptune appears on coins and monuments as a patron of fleets and of victory at sea. The double history is characteristic of Roman religion: a native god of the life-giving fresh water, honoured at the driest point of the year, overlaid with the grander figure of the Greek sea-lord until the two could no longer be separated.

Neptune's afterlife reaches far beyond Rome. Renaissance and Baroque cities built grand public fountains around him as the personification of controlled, civic water, among them the Fontana del Nettuno in Bologna and Florence's Fountain of Neptune, images that fixed the trident-bearing sea-king in the European imagination long after his temples had fallen. In 1846 the eighth planet was named Neptune after the astronomers Urbain Le Verrier and John Couch Adams independently predicted its position from irregularities in Uranus's orbit and Johann Galle then found it exactly where calculation said it should be, the first planet located by mathematics before it was ever seen, an honour that fittingly went to the god of the unseen deep.