The seventh tree is the oak, the tree of Zeus, Juppiter, Hercules, The Dagda (the chief of the elder Irish gods), Thor, and all the other Thundergods, Jehovah in so far as he was 'El', and Allah. The royalty of the oak-tree needs no enlarging upon: most people are familiar with the argument of Sir James Frazer's Golden Bough, which concerns the human sacrifice of the oak-king of Nemi on Midsummer Day. The fuel of the midsummer fires is always oak, the fire of Vesta at Rome was fed with oak, and the need-fire is always kindled in an oak-log.

When Gwion writes in the Câd Goddeu, 'Stout Guardian of the door, His name in every tongue', he is saying that doors are customarily made of oak as the strongest and toughest wood and that 'Duir', the Beth-Luis-Nion name for 'Oak', means 'door' in many European languages including Old Goidelic dorus, Latin foris, Greek thura, and German tür, all derived from the Sanskrit Dwr, and that Daleth, the Hebrew letter D, means 'Door' - the 'l' being originally an 'r'.

Midsummer is the flowering season of the oak, which is the tree of endurance and triumph, and like the ash is said to 'court the lightning flash'. Its roots are believed to extend as deep underground as its branches rise in the air - Virgil mentions this - which makes it emblematic of a god whose law runs both in Heaven and in the Underworld ... The month, which takes its name from Juppiter the oak-god, begins on June 10th and ends of July 7th. Midway comes St. John's Day, June 24th, the day on which the oak-king was sacrificially burned alive. The Celtic year was divided into two halves with the second half beginning in July, apparently after a seven-day wake, or funeral feast, in the oak-king's honour.

Sir James Frazer, like Gwion, has pointed out the similarity of 'door' words in all Indo-European languages and shown Janus to be a 'stout guardian of the door' with his head pointing in both directions. As usual, however, he does not press his argument far enough. Duir as the god of the oak month looks both ways because his post is at the turn of the year; which identifies him with the Oak-god Hercules who became the door-keeper of the Gods after his death. He is probably also to be identified with the British god Llyr of Lludd or Nudd, a god of the sea - i.e. a god of a sea-faring Bronze Age people - who was the 'father' of Creiddylad (Cordelia) an aspect of the White Goddess; for according to Geoffrey of Monmouth the grave of Llyr at Leicester was in a vault built in honour of Janus. Geoffrey writes:

Cordelia obtaining the government of the Kingdom buried her father in a certain vault which she ordered to be made for him under the river Sore in Leicester (Leircester) and which had been built originally under the ground in honour of the god Janus. And here all the workmen of the city, upon the anniversary solemnity of that festival, used to begin their yearly labours.

Since Llyr was a pre-Roman God this amounts to saying that he was two-headed, like Janus, and the patron of the New Year; but the Celtic year began in the summer, not in the winter. Geoffrey does not date the mourning festival but it is likely to have originally taken place at the end of June ... What I take for a reference to Llyr as Janus occurs in the closing paragraph of Merlin's prophecy to the heathen King Vortigern and his Druids, recorded by Geoffrey of Monmouth:

After this Janus shall never have priests again. His door will be shut and remain concealed in Ariadne's crannies.

In other words, the ancient Druidic religion based on the oak-cult will be swept away by Christianity and the door - the god Llyr - will languish forgotten in the Castle of Arianrhod, the Corona Borealis. This helps us to understand the relationship at Rome of Janus and the White Goddess Cardea who is ... the Goddess of Hinges who came to Rome from Alba Longa. She was the hinge on which the year swung - the ancient Latin, not the Etruscan year - and her importance as such is recorded in the Latin adjective cardinalis - as we say in English 'of cardinal importance - which was also applied to the four main winds; for winds were considered as under the sole direction of the Great Goddess until Classical times.

As Cardea she ruled over the Celestial Hinge at the back of the North Wind around which, as Varro explains in his De Re Rustica, the mill-stone of the Universe revolves. This conception appears most plainly in the Norse Edda, where the giantesses Fenja and Menja, who turn the monstrous mill-stone Grotte in the cold polar night, stand for the White Goddess in her complementary moods of creation and destruction. Elsewhere in Norse mythology the Goddess is nine-fold: the nine giantesses who were joint-mothers of the hero Rig, alias Heimdall, the inventor of the Norse social system, similarly turned the cosmic mill.

Janus was perhaps not originally double-headed: he may have borrowed this peculiarity from the Goddess herself who at the Carmentalia, the Carmenta Festival in early January, was addressed by her celebrants as 'Postvorta' and 'Antevorta' - 'she who looks both back and forward'. However, a Janus with long hair and wings appear on an early stater of Mellos, a Cretan colony at Cilicia. He is identified with the solar hero Talus, and a bull's head appears on the same coin. In similar coins of the late fifth century B.C. he holds an eight-rayed disc in his hand and has a spiral of immortality sprouting from his double head. 

Here at last I can complete my argument about Arianrhod's Castle and the 'whirling round without motion between three elements'. The sacred oak-king was killed at midsummer and translated to the Corona Borealis, presided over by the White Goddess, which was then just dipping over the Northern horizon. But from the song ascribed by Apollonius Rhodius to Orpheus, we know that the Queen of the Circling Universe, Eurynome, alias Cardea, was identical with Rhea of Crete; thus Rhea lived at the axle of the mill, whirling around without motion, as well as on the Galaxy. This suggests that in a later mythological tradition the sacred king went to serve her at the Mill, not in the Castle, for Samson after his blinding and enervation turned a mill in Delilah's prison-house.

Another name for the Goddess of the Mill was Artemis Calliste, or Callisto ('Most Beautiful'), to whom the she-bear was sacred in Arcadia; and in Athens at the festival of Artemis Brauronia, a girl of ten years old and a girl of five, dressed in saffron-yellow robes in honour of the moon, played the part of sacred bears. The Great She-bear and Little She-bear are still the names of the two constellations that turn the mill around. In Greek the Great Bear Callisto was also called Helice, which means both 'that which turns' and 'willow-branch' - a reminder that the willow was sacred to the same Goddess ...