Dowth is possibly the oldest of the three great mounds of the Brú na Bóinne complex, and is the least explored in terms of modern archaeology. It has two known passages, on its southwestern side, one of which has an alignment towards setting sun on the winter solstice. The mound was partly excavated in the 1840s, a disastrous archaeological expedition which wrought serious damage to the mound. It is thought the great cairn has a total of 115 kerb stones, although many of them remain buried. Its most famous kerb, known as the Stone of the Seven Suns, is one of a handful that are exposed.
There are two passages at Dowth, which is about the same age as Newgrange and Knowth. One passage is aligned such that the sun can enter into its chamber in winter, and on winter solstice, at sunset, the sun beam strikes an orthostat at the rear of its circular chamber. The other passage, which is cruciform in shape, is blocked by a concrete entrance shaft, but may have been aligned towards Samhain/Imbolc (November and February cross quarter) sunset. Dowth was excavated, albeit very badly, in the late 1840s by R.H. Firth of the Royal Irish Academy. No report of the excavation survives, except whatever notes Firth took during the work. The excavation caused considerable damage to the monument.
Astronomy at Dowth
Pictured above is one of the most beautiful, and indeed well-known, Neolithic carvings from ancient Ireland. It is kerb stone 51, located on the eastern side of the great kerb around the cairn of Dowth. It contains what appear to be suns, or stars, with rays coming out from the centre, and with the whole surrounded by a circle. There are seven of these suns in total, six of which are contained within circles. Various attempts have been made to explain the meaning of these symbols – some say they are representations of the sun at different times of the year; others say they represent celestial bodies such as comets; others still suggest they are representations of a solar eclipse.
Taurus, the Pleiades, spring equinox and precession
It is to mythology, and particularly the ancient story about how Dowth was built, which reveals an ancient astronomical symbolism which may help to explain something about the meaning of the 'Place of Darkness' (Dowth is from Irish Dubad, meaning "darkness"). The story comes from the Dindshenchas, a collection of ancient stories about Irish placenames, and concerns Bresal Bó-Dibad, who was the ruler of the time.
"In his time there fell a murrain on kine in every place in Ireland, except for seven cows and a bull that increased strength for every farmer in his time. By him is built the solid hill in the likeness of Nimrod's tower, so that from it he might pass to heaven, - that is the cause why it was undertaken". The story continues to tell how Bresal's sister stopped the Sun from moving so that there would be 'no night but bright day' until work reached completion. Unfortunately, they committed incest and the Sun went down . . .
The men of Erin left the task incomplete, saying: ". . . since darkness has fallen upon our work, and night has come on and the day is gone, let each depart to his place. Dubad (darkness) shall be the name of this place for ever." (Source: Metrical Dindshenchas)
Given that there are seven "suns" on kerb 51, and that the mythology about Dowth speaks of a bull and seven cows, it seems possible that the site has some connection with the constellation of Taurus, the bull, which contains the open cluster the Pleiades, otherwise known as The Seven Sisters. This constellation was very important at the time leading up to the construction of the Boyne Valley mounds, as it contained the sun on the spring equinox, that very important moment of the year when the sun's path along the ecliptic crossed the celestial equator heading northwards. It is the sun's position among the zodiac stars at this time which determines the current "age" – i.e. the "Age of Taurus".
Another interesting phenomenon which occurs at this time is what is known to astronomers as a heliacal rising of the Pleiades. This happens when the stars in question rise at the eastern horizon but are quickly lost in the glare of the rising sun. It is interesting to note that the Egyptians, and the Dogon tribe in Africa, among others, used the same Dowth-like sun-wheel symbol to signify a heliacal rising.
If these sun-wheel symbols do represent the heliacal rising of the Pleiades, it tells us something very significant about the Neolithic people – they were aware of the great cycle of precession, the slow wobble of the Earth's axis which causes the celestial pole to shift over time, resulting in the vernal equinox point, that place where the sun crosses the celestial equator, moving backwards, or westwards, through the zodiac over a 25,920-year period. This vernal point moves just one degree (about two widths of the full moon) every 72 years, and spends on average 2,150 years in each of the twelve constellations of the zodiac.
The Metonic Cycle
Another interesting point about these symbols is the amount of strokes, or rays, which appear to emanate from the sun symbols. There are a total of 116 notches, counted on the individual sun-wheels as follows: (1) 14, (2) 14, (3) 17, (4) 14, (5) 18, (6) 15, (7) 24. 116 days represents four synodic periods of the moon, the most basic breakdown of the sequence of the Metonic cycle. If we take out the count for circle three (17 notches) we get 99 notches, which could just be an indicator of the eight-year, 99 synodic lunar month Metonic period.
Inside Dowth North - The oldest cruciform passage
The chamber of Dowth North is an eerie place to be. Hidden from daylight, and sunken into the ground, it is cold, dark and claustrophobic. The modern electrical lights do not work, the chamber is only accessible through a 70-foot souterrain, and the passage orthostats lean together such that when you walk up the passage, you have to squeeze through the stones. It's a strange experience, to say the least. But Dowth North could be the oldest cruciform passage in the Brugh na Bóinne complex, so when I was given a chance to visit, in the year 2000, I grabbed the opportunity..
When he visited Dowth in the late 1890s, antiquarian George Coffey said the construction of this chamber was somewhat similar to Newgrange, but in the case of Dowth North, "the roofing-flags are not corbelled, and, in general, less architectural enterprise is shown". The plan of the chamber, as at Newgrange, is cruciform, but smaller, measuring 11 feet high, and about nine feet in diameter.
The passage is 27 feet long, and the entrance has been reconstructed in more modern times, and indeed intruded upon by a concretre shaft built by the Office of Public Works (OPW) in the early 20th century, so it is impossible to say what the original length of the passage was. It may have been roughly twice its current length, given the fact that the kerb of stones on this side of the Dowth mound is located in the next field.
Old passage, new passage
There are structures at Dowth North which are joined together, but which are separated in date of construction by approximately 4,000 years. The Neolithic passage and chamber seem to be older in date than Newgrange, and possibly Knowth, due to the fact that the passage at Newgrange is more advanced, with water drainage techniques incorporated into its roof structure which were not found at Knowth.
But the souterrain, which is a "microlithic" construction of much smaller stones, probably dates to the latter part of the first century AD, and was built into the mound at Dowth, with its entrance located some 25 metres or so from its terminus near the earlier Neolithic passage.
The interior of Dowth North seems to carry on the astronomical theme present on some of the great kerbstones outside the mound. The chamber stone C7 is particularly well decorated, featuring a number of stellar symbols, concentric circles, a small spiral, linear markings and other features such as small inverted V shapes.
Martin Brennan had suggested that Dowth North may have been oriented towards sunset on the February and November cross-quarter days, but evidence from surveying carried out by archaeologists confirms that this passage was, quite probably, aligned on the minor standstill setting moon in the Neolithic.
The astronomical theme was also picked up by George Coffey a century ago. Coffey noticed that many of the star/sun symbols at Dowth were repeated at Newgrange and Loughcrew.
Although Dowth North does not have the same amount of art as the passages at Knowth, there are still a number of stones which are decorated. The most noticable of these is the spectacularly decorated chamberstone, C19, which is decorated with spirals, serpentine shapes, circles and other features, and features designs on both its front face, and its side face.
Dowth North aligned on Minor Standstill moonset
Passage also accepted beam of sunlight on November-February Cross-Quarter Day
In her 1969 plan of the northern passage of Dowth, Clare O’Kelly worked out the magnetic bearing of Dowth’s northern passage using a line centred on the rear orthostat of the central recess of the chamber passing through the centre of the distance between the two outermost passage orthostats — L1 and R1. This line is marked on the plan below as line (A).
The orientation of the northern passage of Dowth is given as 250 degrees magnetic azimuth in Clare O’Kelly’s 1969 drawing. This may be an old survey, but the alignment of Dowth North has been confirmed by another recent survey. The results point towards the possibility that this passage was, in fact, oriented towards the setting position of the Moon for minor standstill south setting in c3300BC. When the plans were drawn in the 1960s, magnetic north was used rather than true north. According to F. Prendergast and T. Ray (Ancient Astronomical Alignments: fact or fiction?, Archaeology Ireland, Summer 2002), the angular difference is large since magnetic north at the time the plans were drawn was 12˚ west of true north.
So, in order to correct for this error, we must subtract 12 degrees from the magnetic reading, which according to O’Kelly is 250 degrees. This gives us 238 degrees (true), which is bang on to the minor standstill south setting moon for the epoch c3300BC. Using SkyMap (v7), I worked out the azimuth of minor standstill setting for c3300BC at almost exactly 238 degrees azimuth, based on a declination for the moon of -18 degrees 45 arcminutes. (*Note: This is a geocentric azimuth. Correction for topcentric, or local, azimuth, due to parallax means the minor standstill setting may have been as much as a degree south of this azimuth. See Victor Reijs' page for explanation. Even with this one degree of difference, it would not make any change to the conclusion that minor standstill would still shine into the central recess of Dowth North, providing the survey data is accurate).
Based on a flat horizon, and with the correct latitude and longitude for Dowth, that would be the modern equivalent of November 16th sunset. That sunset, as confirmed by observations and photographs by myself and Anne-Marie Moroney, would put a half-visible sun sitting over the entrance of Newgrange – i.e. over the part which, viewed from Dowth, would contain the milky quartz.
The range of azimuths allowed by the passage in its current state is shown in the plan at the top of the page. The northernmost azimuth covered is 245 degrees, which almost certainly would allow the sunset on the November-February (Samhain/Imbolc) cross quarter day to shine onto chamber stone 13 (C13 marked on plan). This northernmost azimuth is marked with the line (B), and the beam itself would have lit up the side of a beautifully carved chamberstone, C19 . The southernmost reach of the range of azimuths is 231 degrees T, which is only a few degrees from winter solstice sunset (Line (C)).
Using SkyMap to bring us back to the 3300BC epoch, I calculated the approximate dates when the sun would begin to shine into the chamber of Dowth North and when it would shine for the last time during its southward run along the horizon towards Winter Solstice. The "first flash" event, when the sun beam first enters the chamber, occurs at 51 days before winter solstice, which would be around the old Samhain cross-quarter event (November/February Cross-Quarter).
The "last flash" occurs just 23 days before winter solstice. At this time, as the sun nears winter solstice and the beam withdraws from the passage of Dowth North, the Winter Solstice beam would be striking off the chamberstones of the southern passage. (See picture on right).
Perhaps the northern passage was used in conjunction with Dowth South to watch the sun's slow progress towards Winter Solstice. In other words, as the sunbeam retreated from Dowth North in the few weeks before Winter Solstice, the beam in Dowth South would be strengthening and illuminating chamberstones C7 and C8. (See plan). This idea has been discussed on the Irish-Stones list, and was first brought to my attention by Charlie Scribner.
Of further significance is the apparent alignment of the central axis of the recess chamber which is accessed from the south recess of the main chamber. This alignment is marked Line (D), and is very close, within a degree and a half, of the sunset position on the May/August (Bealtaine/Lughnasa) cross-quarter day. Because of the wide sweep of this off-chamber, it is more than likely that the Minor Standstill North setting was also a target. It is possible this chamber existed before the rest of Dowth North was built, as part of a smaller site. At Knowth West, the innermost part of the passage is oriented differently to the rest of the passage, and perhaps the builders had a different intent originally. See this page for more details.
This is not a definitive explanation of Dowth North’s orientation, because the outer part of the passage was probably removed during early Christian construction there which saw the additon of a complex souterrain structure which interfered with the original Neolithic structure. Based on the extant passage, it would seem there is a distinct possibility the passage pointed to the Minor Standstill south setting Moon, while it also accepted sunlight on the November/February Cross-Quarter Day which would have illuminated chamberstone 13 (C13).
It is highly probable that an observer, standing in the rear recess of Dowth North looking out through the entrance (barring present-day obstacles) of that passage could see Newgrange in his/her field of view. This is interesting because the central axis of Dowth South points to the Hill of Tara and is oriented towards Major Standstill moonset. So both passages appear to have a central axis which points to either major or minor standstill setting moon, and both of these moonsets occur over other significant ancient sites – Newgrange and Tara.