A special class of diviners existed among the Celts, but the Druids
practised divination, as did also the unofficial layman. Classical
writers speak of the Celts as of all nations the most devoted to, and
the most experienced in, the science of divination. Divination with a
human victim is described by Diodorus. Libations were poured over him,
and he was then slain, auguries being drawn from the method of his fall,
the movements of his limbs, and the flowing of his blood. Divination
with the entrails was used in Galatia, Gaul, and Britain.[856] Beasts
and birds also provided omens. The course taken by a hare let loose gave
an omen of success to the Britons, and in Ireland divination was used
with a sacrificial animal.[857] Among birds the crow was pre-eminent,
and two crows are represented speaking into the ears of a man on a
bas-relief at Compiegne. The Celts believed that the crow had shown
where towns should be founded, or had furnished a remedy against poison,
and it was also an arbiter of disputes.[858] Artemidorus describes how,
at a certain place, there were two crows. Persons having a dispute set
out two heaps of sweetmeats, one for each disputant. The birds swooped
down upon them, eating one and dispersing the other. He whose heap had
been scattered won the case.[859] Birds were believed to have guided the
migrating Celts, and their flight furnished auguries, because, as
Deiotaurus gravely said, birds never lie. Divination by the voices of
birds was used by the Irish Druids.[860]

Omens were drawn from the direction of the smoke and flames of sacred
fires and from the condition of the clouds.[861] Wands of yew were
carried by Druids--"the wand of Druidism" of many folk-tales--and were
used perhaps as divining-rods. Ogams were also engraved on rods of yews,
and from these Druids divined hidden things. By this means the Druid
Dalan discovered where Etain had been hidden by the god Mider. The
method used may have been that of drawing one of the rods by lot and
then divining from the marks upon it. A similar method was used to
discover the route to be taken by invaders, the result being supposed to
depend on divine interposition.[862] The knowledge of astronomy ascribed
by Caesar to the Druids was probably of a simple kind, and much mixed
with astrology, and though it furnished the data for computing a simple
calendar, its use was largely magical.[863] Irish diviners forecast the
time to build a house by the stars