wheels.  In Irish texts a Druid is called Mag Ruith, explained as magus rotarum, because he made his Druidical observations by wheels.[1136] This may point to the use of such amulets in Ireland.  A curious amulet, connected with the Druids, became famous in Roman times and is described by Pliny.  This was the “serpents’ egg,” formed from the foam produced by serpents twining themselves together.  The serpents threw the “egg” into the air, and he who sought it had to catch it in his cloak before it fell, and flee to a running stream, beyond which the serpents, like the witches pursuing Tam o’ Shanter, could not follow him.  This “egg” was believed to cause its owner to obtain access to kings or to gain lawsuits, and a Roman citizen was put to death in the reign of Claudius for bringing such an amulet into court.  Pliny had seen this “egg.”  It was about the size of an apple, with a cartilaginous skin covered with discs.[1137] Probably it was a fossil echinus, such as has been found in Gaulish tombs.[1138] Such “eggs” were doubtless connected with the cult of the serpent, or some old myth of an egg produced by serpents may have been made use of to account for their formation.  This is the more likely, as rings or beads of glass found in tumuli in Wales, Cornwall, and the Highlands are called “serpents’ glass” (glain naidr), and are believed to be formed in the same way as the “egg.”  These, as well as old spindle-whorls called “adder stones” in the Highlands, are held to have magical virtues, e.g. against the bite of a serpent, and are highly prized by their owners.[1139]

Pliny speaks also of the Celtic belief in the magical virtues of coral, either worn as an amulet or taken in powder as a medicine, while it has been proved that the Celts during a limited period of their history placed it on weapons and utensils, doubtless as an amulet.[1140] Other amulets—­white marble balls, quartz pebbles, models of the tooth of the boar, or pieces of amber, have been found buried with the dead.[1141] Little figures of the boar, the horse, and the bull, with a ring for suspending them to a necklet, were worn as amulets or images of these divine animals, and phallic amulets were also worn, perhaps as a protection against the evil eye.[1142]

A cult of stones was probably connected with the belief in the magical power of certain stones, like the Lia Fail, which shrieked aloud when Conn knocked against it.  His Druids explained that the number of the shrieks equalled the number of his descendants who should be kings of Erin.[1143] This is an aetiological myth accounting for the use of this fetich-stone at coronations.  Other stones, probably the object of a cult or possessing magical virtues, were used at the installation of chiefs, who stood on them and vowed to follow in the steps of their predecessors, a pair of feet being carved on the stone to represent those of the first chief.[1144] Other stones had more musical virtues—­the “conspicuous stone” of Elysium from which arose a hundred strains, and the melodious stone of Loch Laig.  Such beliefs existed into Christian times.  S. Columba’s stone altar floated on the waves, and on it a leper had crossed in the wake of the saint’s coracle to Erin.  But the same stone was that on which, long before, the hero Fionn had slipped.[1145]