According to legendary history, Castor and Pollux were the sons of Leda and the brothers of Helen of Troy. These twins were noted near and far for their bravery and had divine honors paid to them both in Sparta and in Rome. Their boyhood days were spent on Mount Pelion under the guidance of the wise centaur Chiron, but they spent most of their manhood adventuring, one of their best known exploits being the journey after the Golden Fleece on the ship Argo. During this journey a great storm arose and the frail little bark, whose only power was its fifty oars and the strong arms of the heroes, was tossed about like a shell. Orpheus, with his magic harp, sought to calm the waters and soothe the fears of the oarsmen, and had just about succeeded when two stars suddenly shone above the heads of the twins. This, of course, was static electricity, which sometimes appears like two stars of light attaching itself to each mast, but the Greeks considered it a sign from Jupiter that all was well and that there was nothing to fear from the storm. The Argo went on in safety, and ever after lights at the mastheads were called "Castor and Pollux" and sailors predict fair weather from their appearance.
"The Greeks called them Castor and Pollux—which some call Hermes fire; Saint Elmo others."
—Sir T. Herbert.
Sometimes, however, but one light is seen. This is then called "Helena," after their sister, and is regarded as foreboding a storm.
As a reward for their great affection (for the twins even shared their immortality together since only one was immortal), Jupiter placed them among the stars under the name of Gemini, and the two bright stars in this constellation were placed upon their brows. Sailors love these stars for they are well above the eastern horizon during the first part of January and are visible during the remainder of the stormy season of the year. They watch them and know that if both stars are visible at the same time, the weather is clearing.
"Thus the twins, indulgent save
The shatter'd vessel from the wave."
—Idyllium XXII (FAWKE'S Trans.)
If the storm continues to rage and the stars remain hidden behind the clouds
"sailors trembling
Call on the twins of Jove with prayer and vow."