St. Patrick's equinox journey - a precise alignment across Ireland

St. Patrick's equinox journey - a precise alignment across Ireland

An investigation of some of the prominent places associated with Ireland's patron saint, Saint Patrick, and associated mythology, cosmology and alignments, throws up some very interesting surprises. Anthony Murphy of Mythical Ireland investigates some of the myths behind the man, and his journey across Ireland.

Popular tradition says that Saint Patrick arrived in Ireland at the Boyne Estuary, anciently known as Inber Colpa, before making his way to the Hill of Slane, where probably his most significant act on this island was said to have been performed – the lighting of the Paschal Fire.

The Hill of Slane, where St. Patrick and his first bishop, Cianán, are said to have lit the paschal fire.

Now this first tradition – that of his arrival at Inber Colpa – is interesting. It is interesting because, as one who was arriving into (dare one suggest 'invading?') Ireland, he was following the footsteps of another foreigner who had come ashore, according to our oldest traditions preserved in Lebor Gabála Érenn (commonly called the Book of Invasions), at exactly the same spot.

The first one to put his foot on the shore of Inber Colpa, says Lebor Gabála, was Amergin Glúngeal, poet and spiritual figurehead of the sons of Míl, a band of brothers whose father was the king of Spain. They were, very much, an invading force, who were attempting to take Ireland from the ruling deities, the Tuatha Dé Danann. They were successful in this exploit, by the way.

Just as the arrival of the Milesians to Inber Colpa did not represent their first coming ashore to Ireland, Patrick's arrival at Inber Colpa did not mark his first visit here. He is said to have landed first at Inbher Dé (now Wicklow Harbour) before taking to the sea again and sailing to the northern parts of Ireland.

Symbolic landing

However, the effecting of a landing at Inber Colpa seems to have been a significant symbolic event. What better place for the Milesians to arrive, than the entrance to the most illustrious of all Ireland's rivers, upon whose banks stand the great monuments of Brú na Bóinne, said to have been built by the gods themselves, the Tuatha Dé Danann, even their chief, the Dagda? Amergin had calmed the sea storm and invoked the island of Ireland. He had communed with the three tutelary or sovereignty goddesses - Banba, Fotla and Ériu, offering to each of them to name Ireland for them.

Patrick, in coming to Ireland, was also leading what would be a very major spiritual upheaval, replicating to some degree the exploits of the Milesians, who according to the Annals of the Four Masters had arrived in 1694BC. Patrick was "borne well and prosperously to the harbour of the Mouth of the Colpdi ...", in other words to the Boyne Estuary. (Concannon, p. 105), in March of the year 433AD.

From Inber Colpa, Patrick made his way towards Slane by road. What is not clear is whether he stopped along his way, in Drogheda. Popular folk tradition in Drogheda suggests that Patrick baptised the town's inhabitants at a stone, called Clogh-Patrick (literally, Patrick's stone) on the Collon Road. Historians place this event in 443, at least a decade after his arrival at Colpe. The official histories suggest Patrick went straight from Inber Colpa to the Hill of Slane.


At Slane, Patrick planned to celebrate Easter, which fell in that year (433) on 26th March. This happened to be around the same time as a significant pre-Christian celebration at Tara, marked by a great assembly and a druid festival involving "many incantations and magical devices" to celebrate the "birthday of the year", the rebirth of vegetation.

One of the ceremonies involved in this great assembly was the "striking forth of new fire" and there was a proscription, enforceable the death penalty, upon the lighting of any other fire in any hearth in Eire until the "druid spark should be drawn by friction from the sacred wood on the royal heights of Tara".

Now the history books tell us that Saint Patrick "had probably some special reason for his selection of Slane, thought what it was does not transpire". We may be able to provide an answer (we, in this case, being Richard Moore and I. We first wrote about this in our book Island of the Setting Sun: In Search of Ireland's Ancient Astronomers).

The rest of this part of the story is, as they say, history. Patrick ordained the first priest in Ireland, St. Cianán of Duleek, and Cianán lit the huge pyre on the top of the Hill of Slane, kindling "a fire which in Eire shall not be extinguished for ever".

Laoghaire the High King, was greatly vexed when the whole sky above Bregia (the ancient name of the area around Slane and Tara) "brightened with a lumination fairer than that of day". One of Laoghaire's druids or magicians said to him:

Unless yonder fire be this night extinguished, he who lighted it, will, together with his Followers, reign over the whole island.

Astronomical symbolism

The position of Slane relative to Tara and indeed to Inber Colpa and Drogheda is of significant interest in this exploration, as is the astronomical symbolism which becomes apparent on investigation of various aspects of the Milesian arrival and the coming of Saint Patrick.

Although there is nothing that I can find in the local traditions of Drogheda to directly connect Saint Patrick to the eminent monument known as Millmount, which has dramatic views over the ancient river Boyne and the town, and indeed the estuary, this is the place according to folklore where Amergin was buried. It is the principal ancient monument of Drogheda, long thought to have been originally raised by the Normans in the 12th century but, as the result of archaeological investigations in the past decade, is now believed to possibly be a prehistoric burial mound.

The mound at Millmount is topped by a martello tower built by the British army in 1808.

From the mound of Millmount, the sun sets directly into the Hill of Slane on 24th March every year. This is fascinating, because this date falls between the Vernal Equinox, which usually falls on 20th March, and the date upon which Patrick lit the Paschal Fire at Slane (26th March). Many scholars and astronomers know that the date of Easter is tied to the equinox and is calculated according to the first full moon after Vernal Equinox.

The Song of Amergin and sunset at Inber Colpa (Boyne Estuary).

Lebor Gabála Érenn tells us that Amergin landed at Inber Colpa on the seventeenth day of the moon (i.e. when the moon was full), "on the kalends of May" (i.e. coinciding with the ancient festival of Bealtaine, a fire festival marking the beginning of summer and the bright half of the year). Using astronomy software to "wind the clock back" and have a look at the sky at Bealtaine in 1694BC, Richard Moore and I were confronted with a stark image when researching Island of the Setting Sun.

The poet and astronomer Amergin said "Who but I knows the place where the sun sets? Who but I knows the ages of the moon? At the moment he placed his foot on the shore of the Boyne at Inber Colpa, the sun was in the hand of the great constellation we know today as Orion. Readers of Island of the Setting Sun will know this is very significant. The symbolism is stark. The great "man of the sky" is carring the globe of the sun, his hand immersed in the Milky Way, the heavenly Boyne. One of the Irish names for the Milky Way is Bealach na Bó Finne, the Way of the White Cow. The name of the Boyne has the same derivation, from the White Cow.

Orion (Amergin) with the sun in his hand on the day the Milesians set foot on the shore of the Boyne. Note that Orion's foot is at the shore of the river constellation Eridanus, while the other river, the Milky Way, has the sun in it.

Because the full moon is always opposite the sun, we know that the moon was also in the Milky Way on the day the Milesians were said to have arrived. There are only two places in the sky where the path of the sun, moon and planets (known as the ecliptic) crosses the Milky Way. One is above Orion. The other is beneath Ophiuchus, the serpent-bearer.

Fast-forward to 26th March 433AD, when we are told Patrick lit the fire at Slane. Just before sunrise on that morning, the just-past-full moon was beneath Ophiuchus. The moon sets in the southwest, but the constellation Ophiuchus – depicting a hero grappling with a giant serpent (this imagery is VERY significant) – sets over Slane as viewed from Millmount.

Ophiuchus, the serpent-bearer, descends into Slane viewed from Drogheda, 26th March 433AD.

The Paschal Fire was lit, we are told, at dusk on that day. Using popular astronomy software, we can see that at the moment the Paschal Fire is kindled, after the sun has set into Slane viewed from the east, the stars of Orion become visible and then he, the giant man, descends slowly into the Hill of Slane.

Orion chases the sun into the Hill of Slane on the evening of March 26th 433AD, viewed from Drogheda.


It is interesting that these two giant "men" of the sky, Orion and Ophiuchus, the "warrior" and the "healer" are not only in opposition to each other, but they both appear to guard the great "starlit ford of night", where the Milky Way is crossed by the sun and moon.

Heading west

Although Patrick did not proceed from Slane directly to Cruachan Aigle (Croagh Patrick) in the west, it is in this direction that our inquiry takes us, led by the setting sun and the alignments. In fact, Patrick's journeys after Slane are not easy to trace. He visited Tara, and Meath, Connacht and Ulster.  

On the peak of the Hill of Slane, shrouded in trees, is a mound or motte, said to be the burial place of an ancient king of the Fir Bolg (another race who arrived here in prehistory, according to Lebor Gabála) called Sláine. It is this king from whom Slane is named. Watching those sunsets in the days around spring equinox years ago, Richard Moore and I were struck by a desire to find out where that sun might lead us.

The alignment from Millmount through Slane to Croagh Patrick is 136 miles or 217km long.


In around the year 2004, I first used Google Earth and was fascinated by the ability to use its ruler tool to draw lines (they are more accurately described as arcs, because they follow the earth's curvature) between monuments across huge distances. Imagine my surprise, indeed my astonishment, when I used the ruler to draw a line between Millmount and the Slane mound, and extending it further west, to see where it would lead, I found that after a great distance (c. 136 miles or 218 kilometres), it landed precisely on the peak of Croagh Patrick.

The Millmount-Slane alignment continues precisely to the church on the summit of Croagh Patrick - a distance of almost 136 miles.


The alignment passes through some significant places on the way, not least the mysterious Hill of Mael with its impressive trivallate hillfort. 

The Hill of Mael with its ringfort (cashel) and trivallate hillfort is precisley on the Millmount-Slane-Croagh Patrick alignment.

There is a long-standing folk tradition associated with St. Patrick which suggests that he was responsible for banishing snakes from Ireland. The constellation Ophiuchus represents the serpent-bearer, the mythical Aesculapius who grasps the snake with both hands. Of further symbolic interest here is the fact that the shape of the serpent-bearer constellation, if you take away the head and tail of the serpent, represents the bishop's mitre worn by Patrick, hence his epithet 'Adze Head'.

The cosmology mimics what happens in Patrick's story – he comes from the east, carrying the torch, the "new flame" of Christianity, and heads out to the west, along a route closely aligned with Vernal Equinox and the date of his first fire, towards the holy mountain where he battled with demon birds, and from which he is said to have banished the snakes.

Fascinatingly, the alignment from the Boyne Estuary through Slane and Mael skirts Rathcroghan on its way west, and the Tóchar Phadraig, the old pilgrim route which the saint himself was said to have followed, from Aghagower to the Reek, meanders along this great east-west alignment. In fact, Ballintubber, Killavally and Aghagower all straddle the alignment. I am tempted to suggest that at one time the Tóchar Phadraig might have stretched all the way from Inber Colpa to Croagh Patrick, but I think the imagination has been stretched far enough for now!

Illumination of 5,000-year-old megalithic art on the Equinox Stone at Cairn T, Loughcrew.


Before I leave the subject for now (I feel that there will be further posts about this, as I haven't yet touched upon the Tara-Slane alignment and the significant symbolism involved there) I must take you to the hills of Loughcrew in northwestern Meath to add one more piece to a complex puzzle. The Millmount-Croagh Patrick line skirts by the hills of Loughcrew, to the south. But inside the Hag's Cairn on Slieve na Calliagh, known today as Cairn T, I made an interesting observation years ago which adds to the intrigue. Situated in the rear recess of the chamber (sadly, it is now closed to the public due to concerns over possible subsidence), with my back to the famous 'Equinox Stone' which is lit beautifully by the golden rays of the dawn sun at the equinoxes, looking out through the entrance of the passageway, I found I was looking back to the Hill of Slane in the east. At Cairn T, over 5,000 years ago, ancient astronomers observed the equinox dawns from their stone chamber, and as they did so they were looking at towards Slane. It seems that the latter's association with equinox is much older than our friend Saint Patrick.

To be continued ...


Concannon, Mrs. Thomas, Saint Patrick: His Life and Mission, Talbot Press,1931.

D'Alton, John, History of Drogheda, Volumes I & II,1844.

Macalister, R.A. Stewart, Lebor Gabála Érenn, Part V, Section VIII: The Sons of Mil, Irish Texts Society, 2008 [1956].

Murphy, Anthony and Moore, Richard (2006), Island of the Setting Sun – In Search of Ireland's Ancient Astronomers, The Liffey Press.

Swift, Edmund L., The Life and Acts of Saint Patrick, Hibernia Press Company,1809.

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