Neptune

Neptune is best known as the Roman god of the sea, but his oldest and most distinctly Roman domain was fresh water, the springs, streams and standing water on which farming and the city depended. His festival, the Neptunalia, fell on the twenty-third of July, at the height of summer when water was scarcest and most precious, and Romans built leafy shelters and drew water in a rite plainly aimed at the drought. Only through his thorough identification with the Greek Poseidon did Neptune acquire the wider portfolio for which he is now famous: lordship of the sea, of earthquakes, and of horses.

Neptune's oldest Roman temple, built after Rome's naval victory over Carthage in the First Punic War and standing near the Circus Flaminius, shows how quickly the god's maritime side developed once Rome became a sea power, even though the cult began, as the Neptunalia's midsummer date suggests, as a plea against drought rather than a prayer for calm seas. Equestrian games held at his festival tie him to the domain of horses that later, through the Greek Poseidon Hippios, became fully attached to him once the two gods were merged, since a Roman audience already linked Neptune with chariot racing before the identification was complete.

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.