Onagh : Portal Tomb

CountyWicklow
Grid RefO 197 153
GPSO 19673 15279 (7m)
Longitude6° 12' 36.01" W
Latitude53° 10' 28.36" N
ITM east480366
ITM north584435
Nearest TownKilmacanoge (5.1 Km)
OS Sheet56
UTM zone29U
UTM x449041
UTM y5761192

This site has subsites

Glaskenny - Rock OutcropOnagh - Rock Art
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Visit Notes

Saturday, 25th August 2001

This took some effort to find due to being situated in a dip, down a bank from a single track road. I had to ask for directions to it while I was standing just 100 yards away.

After a quick field scramble and barbed wire fence hop we reached it. The capstone has slid off and sits resting against the rear of the chamber and the floor at 45 degrees. The chamber itself is collapsed and one of the portal stones has fallen, lying beneath the hedgerow.

The overgrown nature of the field that it sits in both adds and subtracts from this great tomb. The hedgerow around it is studded with smaller stones that form an arc just to either side. Was this a courtyard?

The large rock used to form the roof of a portal tomb or kist.

A compartment in a tomb in which burials were placed. In court tombs and wedge tombs a chamber is a sub-division of the burial gallery. Portal tombs have single chambers and passage tombs can have anything from one to five chambers, although usually passage tombs are considered to have a main chamber with extra subsidary chambers.

Portal stones are a pair of upright stones that form the 'entrance' to a portal tomb. They are usually well matched, being of even dimensions. As well as forming this doorway they also act as the front support for the capstone and are usually taller than the stones that form the chamber.

Often there is a door stone in between them blocking off access to the chamber within.

Click Thumbnail to View Full Size Image

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Sunday, 6th January 2002

Having had a poor day I decided to see if the dead winter vegitation around this tomb had made it more visible. Luckily it has exposed this structure significantly and I was able to take some clearer photos.

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Saturday, 20th July 2002

I am always in awe of the size of this capstone. It is easily 3m x 3.5m, making it a very large example. Anthony, despite the tombs run down condition, was also taken in by its charm and impressive dimensions.

Tuesday, 27th December 2005

For a long time I have suspected that there is a significant winter solstice alignment at this site. Many people have looked at me as if I was from another planet when I've mentioned this possibility, but today I decided to go out and see for myself.

After making a last minute decision to go out I wasn't sure if I would get there in time. Panic set in as I drove along the road to the site and could see a bright orange glow in the wrong place! Oh well, I thought, I might as well go anyway. I arrived in time for the sunrise and the glow was now in the right place: the bendy roads had completely disoriented me.

The sun, although partly hidden by broken clouds, broke the horizon at the lowest point on the hillside to the southwest of the portal tomb . Result!

While I was here I took the time to take some compass readings. I now think there are two other alignments from this site, which I hope to check out next year.

Portal tombs are what most people wrongly refer to as dolmens. They are, to me at least, the most strikingly designed of the megalithic tombs. They are called portal tombs because they have two large upright stones, usually very well matched, in front of the chamber that seem to form a doorway.

Resting upon the portal stones and the chamber a large capstone rests (sometimes there are two capstones - see Knockeen (County Waterford)), usually at an angle of around 22 degrees from the horizontal. Although these were originally incorporated into one end of a long cairn there are none left in this state today, although traces of the cairn can sometimes be seen upon the ground. The portal stones can be up to 3.5m tall, which combined with a thick capstone can produce an imposing monument over 5m tall. Capstones can reach in excess of 70 tonnes, with that of Browne's Hill (County Carlow) being estimated at over 120 tonnes.


Often betwen the portal stones there is a door slab, blocking the width of the entrance, but not always the full height. Door slabs are either half height, three quarter height or full height, describing the amount of the portal that they obstruct. All portal tombs would have had door slab, but this has often been removed to facilitate entry into the chamber.

Quite rarely the portal stones are the same height as the chamber and the characteristic slope of the capstone is created by the profile of the capstone (see Glendruid (County Dublin)).

Saturday, 19th May 2007

This was a flying visit to see what state the monument is in. Someone had told me that the nearby farmhouse was up for redevelopment, so I wanted to see what was going on.

The field is a mess. The cottage has gone and demolition debris litter the field. The tomb is more overgrown than I've ever seen it and some rubbish has been piled up near it. I hope the developers know what these large rocks on the edge of the site are!

Click Thumbnail to View Full Size Image

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Marked Sites

Directions

From Enniskerry take the Glencree Road and take the first left. Turn right at the next junction and the tomb in in a field on the left after about 300m, next to a deserted house with a red tin roof.

Random Gazetteer

A Selection of Other Portal Tombs

About Coordinates Displayed

This is an explanation of (and a bit of a disclaimer for) the coordinates I provide.

Where a GPS figure is given this is the master for all other coordinates. According to my Garmin these are quite accurate.

Where there is no GPS figure the 6 figure grid reference is master for the others. This may not be very accurate as it could have come from the OS maps and could have been read by eye. Consequently, all other cordinates are going to have inaccuracies.

The calculation of Longitude and Latitude uses an algorithm that is not 100% accurate. The long/lat figures are used as a basis for calculating the UTM & ITM coordinates. Consequently, UTM & ITM coordinates are slightly out.

UTM is a global coordinate system - Universal Transverse Mercator - that is at the core of the GPS system.

ITM is the new coordinate system - Irish Transverse Mercator - that is more accurate and more GPS friendly than the Irish Grid Reference system. This will be used on the next generation of Irish OS maps.

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