The old Welsh translation means "fire globe." They were hand-blown spheres of deep blue/green glass, varying in size from that of a hand to a basketball. At their top was a round hold and a candle was positioned at the inside bottom. A knoted network of leather cord/rope provided suspension from the hand or (more commonly) branshes of trees. They were used on any of the 4 cross-quarter/Lunar High Holy Days, and were hung en masse from lower tree branches, when all were asembled, to illuminate the Ritual Area in an erie glow.
Druids wore white robes b/c they wished to radiate light, to "stand apart" from the world, and demonstrated this by working within a sea of this "ultra-vilet" light, which high-lighted the while above all others.
The Colbalt Light was also used to attract the Otherworld forces as well.
