Adder stone is a type of stone, usually glassy, with a naturally occurring hole through it. Such stones have been discovered by archaeologists

Archaeology

Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...

 in both Britain

Great Britain

Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

 and Egypt

Egypt

Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...

.

In Britain they are also called hag stones, witch stones, serpent's eggs, snake's eggs, or glain neidyr in Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

, milpreve in Cornwall

Cornwall

Cornwall is a unitary authority and ceremonial county of England, within the United Kingdom. It is bordered to the north and west by the Celtic Sea, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Cornwall has a population of , and covers an area of...

, adderstanes in the south of Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 and Gloine nan Druidh ("Druids' glass" in Scottish Gaelic) in the north. In Egypt they are called aggry or aggri.

Adder stones were believed to have magical

Magic (paranormal)

Magic is the claimed art of manipulating aspects of reality either by supernatural means or through knowledge of occult laws unknown to science. It is in contrast to science, in that science does not accept anything not subject to either direct or indirect observation, and subject to logical...

 powers such as protection against eye diseases or evil charms, preventing nightmare

Nightmare

A nightmare is an unpleasant dream that can cause a strong negative emotional response from the mind, typically fear or horror, but also despair, anxiety and great sadness. The dream may contain situations of danger, discomfort, psychological or physical terror...

s, curing whooping cough

Pertussis

Pertussis, also known as whooping cough , is a highly contagious bacterial disease caused by Bordetella pertussis. Symptoms are initially mild, and then develop into severe coughing fits, which produce the namesake high-pitched "whoop" sound in infected babies and children when they inhale air...

, the ability to see through fairy or witch disguises and traps if looked at through the middle of the stone, and of course recovery from snakebite

Snakebite

A snakebite is an injury caused by a bite from a snake, often resulting in puncture wounds inflicted by the animal's fangs and sometimes resulting in envenomation. Although the majority of snake species are non-venomous and typically kill their prey with constriction rather than venom, venomous...

. According to popular conception, a true adder stone will float in water.

Three traditions exist as to the origins of adder stones. One holds that the stones are the hardened saliva

Saliva

Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...

 of large numbers of serpents

Snake

Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

 massing together, the perforations being caused by their tongues. The other 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 (and much easier to attain). It details that the stone can be any rock with a hole bored through the middle by water. Human intervention (ie, direction of water or placement of the stone) is not allowed.

Adder stone was in high esteem amongst the Druid

Druid

A druid was a member of the priestly class in Britain, Ireland, and Gaul, and possibly other parts of Celtic western Europe, during the Iron Age....

s. It was one of their distinguishing badges, and was accounted to possess the most extraordinary virtues. There is a passage in Pliny

Pliny the Elder

Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...

’s Natural History, book xix, minutely describing the nature and the properties of this amulet. The following is a translation of it:

"There is a sort of egg

Egg (biology)

An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...

 in great repute among the Gauls

Gauls

The Gauls were a Celtic people living in Gaul, the region roughly corresponding to what is now France, Belgium, Switzerland and Northern Italy, from the Iron Age through the Roman period. They mostly spoke the Continental Celtic language called Gaulish....

, of which the Greek writers

Greek literature

Greek literature refers to writings composed in areas of Greek influence, typically though not necessarily in one of the Greek dialects, throughout the whole period in which the Greek-speaking people have existed.-Ancient Greek literature :...

 have made no mention. A vast number of serpents

Snake

Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

 are twisted together in summer, and coiled up in an artificial knot by their saliva

Saliva

Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...

 and slime; and this is called "the serpent's egg". The druids say that it is tossed in the air with hissings and must be caught in a cloak before it touches the earth. The person who thus intercepts it, flies on horseback; for the serpents will pursue him until prevented by intervening water. This egg, though bound in gold

Gold

Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 will swim against the stream. And the magi are cunning to conceal their frauds, they give out that this egg must be obtained at a certain age of the moon

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

. I have seen that egg as large and as round as a common sized apple

Apple

The apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family . It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Apple grow on small, deciduous trees that blossom in the spring...

, in a chequered cartilaginous

Cartilage

Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

 cover, and worn by the Druids. It is wonderfully extolled for gaining lawsuits, and access to kings. It is a badge which is worn with such ostentation, that I knew a Roman

Ancient Rome

Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

 knight

Knight

A knight was a member of a class of lower nobility in the High Middle Ages.By the Late Middle Ages, the rank had become associated with the ideals of chivalry, a code of conduct for the perfect courtly Christian warrior....

, a Vocontian, who was slain by the stupid emperor

Roman Emperor

The Roman emperor was the ruler of the Roman State during the imperial period . The Romans had no single term for the office although at any given time, a given title was associated with the emperor...

 Claudius

Claudius

Claudius , was Roman Emperor from 41 to 54. A member of the Julio-Claudian dynasty, he was the son of Drusus and Antonia Minor. He was born at Lugdunum in Gaul and was the first Roman Emperor to be born outside Italy...

, merely because he wore it in his breast when a lawsuit was pending."

Huddleston's edition of Toland 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.