An adder stone is a type of stone, usually glassy, with a naturally occurring hole through it. Such stones have been discovered by archaeologists in both Britain and Egypt. Commonly, they are found in Northern Germany at the coasts of the North and Baltic Seas. In Britain they are also called hag stones, witch stones, serpent's eggs, snake's eggs, or Glain Neidr in Wales, milpreve in Cornwall, adderstanes in the south of Scotland and Gloine nan Druidh in the north. In Germany they are called Hühnergötter. In Egypt they are called aggry or aggri. Three traditions exist as to the origins of adder stones. One holds that the stones are the hardened saliva of large numbers of serpents massing together, the perforations being caused by their tongues. The second claims that an adder stone comes from the head of a serpent or is made by the sting of an adder. The third is more modern. It details that the stone can be any rock with a hole bored through the middle by water. Human intervention is not allowed.
The Druids
Adder stone was held in high esteem amongst the Druids. It was one of their distinguishing badges, and was accounted to possess the most extraordinary virtues. There is a passage in Pliny’s Natural History, book XXII, describing the nature and the properties of this amulet. The following is a translation of it: Huddleston's edition of John Toland's "History of the Druids" gives some very ingenious conjectures on the subject of this very enigmatical Druids' egg. The amulets of glass and stone, which are still preserved and used with implicit faith in many parts of Scottish Gaeldom, and are conveyed, for the cure of diseases to a great distance, seem to have their origin in this bauble of ancient priestcraft.
The Glain Neidr or Maen Magi of Welsh folklore is also closely connected to Druidism. The Glain Neidr of Wales are believed to be created by a congress of snakes, normally occurring in spring, but most auspicious on May Eve. Although not named as Glain Neidr, magic stones with the properties of adder stones appear frequently in Welsh mythology and folklore. The Mabinogion, translated into English in the mid-nineteenth century by Lady Charlotte Guest, mentions such stones on two occasions. In the story of Peredur son of Efrawg, in a departure from Chrétien de Troyes' Perceval, the Story of the Grail, Peredur is given a magical stone that allows him to see and kill an invisible creature called the Addanc. In another tale, Owain, or the Lady of the Fountain, the hero Owain mab Urien is trapped in the gatehouse of a castle. He is given a stone by a maiden, which turns Owain invisible, allowing him to escape capture.
Serpents, not being present in Ireland, don't often feature in Irish mythology, yet other creatures can form parallels. The legendary druid Mug Ruith was said to have a stone which could turn into a poisonous eel when thrown in water, this may be a reference to an Adder Stone.
In Russian folklore, adder stones were believed to be the abodes of spirits called Kurinyi Bog. Kurinyi Bog were the guardians of chickens, and their stones were placed into farmyards to counteract the possible evil effects of the Kikimora Kikimora, who also guarded and took care of chickens, could often unleash misery upon hens they did not like by plucking out their feathers.
