Gravitational Attraction

A little while ago the European Space Agency launched GOCE, its gravity mapping satellite. GOCE stands for Gravity field and steady-state Ocean Circulation Explorer. It is already in orbit but in a couple of weeks its batteries will be fully charged-up, its systems calibrated and its work will begin. Unlike a typical satellite, with spindly aerials, disks, and protruding panels, this satellite is streamlined and sleek. GOCE needs aerodynamic features because it will fly at only 250km above the surface of the Earth, lower than most Earth orbiting satellites, and will encounter wisps of atmosphere. It will plot the earth’s gravitational field to a higher level of accuracy than we are currently able.


GOCE's mission will require a high level of stability, hence the fins and its ion-propulsion engine. See an animation here: www.esa.int/SPECIALS/GOCE_animation/

Things have different weights when in different places. The gravitational attraction an object experiences, its desire to rush to the centre of the earth, is effected by the presence of irregularities in the shape of the earth, the uneven distribution of mass beneath the crust, and the presence of mountains or even large buildings. The intensity of the desire varies and the GOCE will map this variable terrain. It will draw a surface of equal gravitational force, sometimes called the geoid, as it dips above and below the Earth's physical surface. A science blogger gives this illustration:

Say you take a one-pound weight, and you walk along the surface of the Earth. If the density of the ground underneath you begins to increase, the gravitational force will increase and the weight will get heavier. To counteract this, you raise the weight up higher - therefore reducing gravity's influence. If, as you walk along, you continue to adjust the height of the weight so that it always weighs one pound, you will be following the surface of the geoid. www.scientificblogging.com/welcome_my_moon_base/goce_aerodynamic_satellite_will_map_geoid

So, those African women carrying supplies on their heads have actually found a way to make the load a fraction lighter. A very small fraction.

One of the most useful outcomes of GOCE’s work will be an increased understanding of the movement of the oceans. But, personally, I am looking forward to the maps. Gravitational forces at play have been mapped before. The difference between standard gravity and the actual gravity found in a certain place is sometimes called the Bouguer anomaly. I examined a Bouguer Anomaly Map of Northern Ireland recently.


From the Bouguer Anomaly map

This is a detail from southern Armagh. It can be seen that Slieve Gullion is a highly positive area. This would probably make a kind of sense to anyone familiar with this mountain. It is a proud and distinguished peak and seems to deserve any form of special attention. Slieve Gullion is an extinct volcano standing apart from other mountains but the highest in the county nonetheless. I wonder if this apartness, free from softening influences, contributes to the large positive Bouguer anomaly wrapped around the mountain. Geologists reckon the strength of this anomaly indicates a high-density mass of rock concealed under the mountain. I can report that, when climbing Slieve Gullion lately, my backpack sure seemed heavier as I approached the peak. But seriously, I wonder could a mountain with a large positive Bouguer anomaly, such as Slieve Gullion, be noticeably more tiring to climb?


Gullion at sunset, image taken from here.

Slieve Gullion’s powerful presence also means it has made frequent appearances in myths, legends, and more recent writings from Northern Ireland. It seems the mountain carries an unusually high cultural weight too. In the meantime we can watch for the GOCE, a fast-moving dot passing 250km above our heads.

Dungannon Exhibition

As part of its arts festival Dungannon borough will host an art exhibition in the old Territorial Army garages on Castlehill. The organisers remark that this exhibition space is a contested site. It has been the high vantage point of local powers for centuries, an O'Neill site, a plantation era townhouse, and most recently a base for the British Army. To reflect this history artists were invited to submit work concerned with the transformation or the claiming of space, either personal or public.



I thought they might like The Map of Watchful Architecture, and sure enough, it has been accepted and will feature in the Art on the Hill exhibition. It runs from 1 May until the 10 May 2009. I will print the map on paper for this show, large.

A 2000 Year Tradition

I want The Map of Watchful Architecture to help us see old structures afresh and new structures in a historical light, bringing new illumination. The map represents certain structures, perhaps built centuries apart, as fundamentally the same. For example, the Border was predicted by the 2nd century structure of the Dorsy, an official entrance into Ulster. Nowadays, just south of the Border the Garda Síochána perform spot checks on buses, looking for illegal migrants. Instead of two categories, 1st Century Gate and 21st Century Immigration Control, my map uses just one: checkpoint. Immigration control is revealed as inheritor of a long tradition while at the same time an ancient site is drawn into the contemporary dynamic.


Detail from The Map of Watchful Architecture 1.0

Adding to the diversity of checkpoints in Ireland is a timber castle discussed in Archaeology Ireland lately (Volume 21, No. 2. Issue No. 80). We are well used to seeing old stone towers in the landscape and it is interesting to realise that once wooden towers dotted the landscape too. None have survived but there is documentary evidence for them. One particular wooden tower is referred to in reports, letters, and we even have an image. In 1575, under the earl of Essex, the English constructed a fort on a strategic crossing-point of the River Blackwater, near modern day Blackwatertown. This construction was to control access in and out of western Ulster. It was the gateway to a contested territory, Hugh O’Neill’s lands in South-East Tyrone.

Apologies for the low quality of this reproduction

On the one side of the Blackwater the tower was of stone. On the other side is an impressive wooden tower, four stories high. It is the darker tower in the above image. Huge uprights at each corner are obviously the major structural features. Note the bridge; it seems to link both towers. Anyone using it certainly had to pass through the right-side structure and possibility the timber tower too. This makes the structure a filtering installation. A sixteen century checkpoint. Part of a long tradition going back, and forward.

Stones of Ulster

The Ulster Historical Foundation’s graveyard database is an interesting find. It is called History from Headstones. Whatever urge has us wandering into old graveyards and reading headstones can now be indulged online. The website is for researchers and the generally interested. You can browse via theme. For example, I selected ‘Geographical’ then narrowed the enquiry to ‘Honduras’ (a former home of mine). Two gravestones in Northern Ireland mention the Central American country. The texts are presented in a graveside manner:


Tombstone in Clifton Street graveyard, in Belfast’s Shankhill, from History from Headstones. This is a highly notable graveyard, a stone-written history of Belfast. Read a BBC article about this graveyard here.

There are maps on the site too. The charted graveyards can be filtered in various ways. With a brief look it seems Catholic, Church of Ireland, and Presbyterian graveyards are fairly evenly spread throughout Northern Ireland, with the exception of Fermanagh’s shortage of Presbyterians.


Coloured dots give the locations of all graveyards in Fermanagh charted by History from Headstones


The four Presbyterian graveyards in Fermanagh

Lately I have been working in the Built Environment Library in the Cathedral Quarter, Belfast. I go there to gather data for The Map of Watchful Architecture. This library is another excellent resource. It has been especially useful for plotting World War II structures. Thank you to all the staff who have helped me. I notice the digital maps I examine there mark famine graves and sites where unbaptised children were buried. In the landscape these sites are usually unmarked, they certainly do not have headstones. So, it is no surprise that History from Headstones does not include these kinds of sites. After death, we may need a stone stood in our stead so not to be forgotten.

But History from Headstones does have the category ‘other.’ This includes Reformed Presbyterian, Non-Subscribing, Moravians, and Quaker. Looking at the maps I wondered if there is any such thing as mixed-denomination graveyards in Northern Ireland. Dr William Roulston, Research Director of the Ulster Historical Foundation, tells me that ‘other’ also includes graveyards of antiquity not associated with any particular denomination now. “For example, graveyards on the site of a former monastery or medieval parish church. Such graveyards can be considered mixed-denomination in the sense that persons of all religious backgrounds lie buried together. There would be around three hundred such graveyards in Northern Ireland.”

It is too bad the database does not extend beyond Northern Ireland into the rest of Ulster. Of course the limitation is understandable, the creators of the database had to stop somewhere. Also, assuming they used some pre-existing information, surveys from both sides of the Border are not always compatible. This is something I am discovering as I continue compiling The Map of Watchful Architecture. Alas, the Built Heritage Library does not have a direct southern equivalent. I bet there were World War II pillboxes built in the southern Border counties too, but this information is not easily accessible.

I will have to keep digging.

Links: The Northern Ireland Environment Agency: Built Environment and the Ulster Historical Foundation's History from Headstones.

Points of control and observation

Here are the military Border structures built and manned during Operation Banner. I have divided them into watchtowers and checkpoints although, as discussed below (20 January), it is not a clear distinction to me. In addition, I use the term ‘checkpoint’ for a fort built by a roadside whereas, as a Newryman told me lately, 'checkpoint' commonly meant any stretch of road the army chose to occupy for a few hours. To many ‘checkpoints’ were movable points where one was pulled-over and questioned.


Border structures, Operation Banner.

I consider this map part of a work in progress rather than a finished piece. I will not be publishing it beyond this blog. Note that it only marks structures reasonably close to the Border, nor does it include RUC stations that may have also housed soldiers.

Watchtower or Checkpoint

A section of the work in progress, The Map of Watchful Architecture.

I am busy plotting the locations of defensive architecture. There are many hundreds of raths (ringforts) along the Border and I do not wish to display them all. One way of cutting back is to only display raths in a narrow Border corridor, one hundred metres for example. But then what to do with uncommon features I do not wish to cut, that fall beyond that confine? For example, there are only about thirty military installations from the recent deployment to display. I would like to display all of them. Is it justifiable to have one rule for raths and another rule for checkpoints and watchtowers? Should I mechanically chart everything evenly, thereby creating a map awash with raths? Or think more aesthetically?

In the design of the Map of Watchful Architecture I seek a middle ground between cartographical accuracy, visual appeal, meaning, and integrity.

I am pretty sure two categories on the map will be ‘Towers’ and ‘Checkpoints.’ Today I went through the coordinates of the 30 recent military installations to define each as either one or the other. I did this by simply looking at its location on a detailed map. If the feature was on a hilltop with no roads nearby then it was clearly a watchtower. If it was right next to a road then it was a checkpoint. However, I found two that seemed to fall between both possibilities. I include the maps here as you never know, one of this blog’s readers might be able to tell me. They are both in Fermanagh, close to roads but not quite on them, and only slightly elevated. Watchtowers or checkpoints?


One and ...


two.

This has me wondering; what was the difference between a tower and a checkpoint anyway? They were both built tall and both bristled with surveillance technology. But did the almost sculptural presence of high watchtowers, over-lording, uncontactable, mean they deserve their own distinct place on the map? By contrast the checkpoints always seemed more ordinary. You saw the men inside. They came out and spoke to you sometimes.

South Armagh had eleven installations. Looking at their locations the danger of deployment in that area is stark. Only one out of the eleven was a roadside checkpoint. The rest were on the peaks of mountains. In South Armagh the army had to stay off low ground, or at least not be on it for long, preferably by using a helicopter. The army’s mission there was containment. The towers seem to have made a net, strung between high points.

On Drumlins

In an earlier entry I promised words about drumlins. The name may come from the Irish droimnín: a little hill ridge. These hills are a lot more common in the north than the south of Ireland and give parts of the North a very distinct look. They are made of layers of loose rock worked by the massive and patient attentions of glaciers or shifting waters, rather like the hard ripples left on a beach at low-tide. They tend to be oval in shape and come in batches, their long axis running parallel and their blunter ends facing into the glacial movement. I have read it described as a “basket of eggs topography.” On a Border walk near Aughnacloy I encountered one perfect example, a smooth green egg lying sideways in the land, fifty metres tall.


Strangford Lough

There are plenty of drumlins in County Down. Those islands in Strangford Lough, they’re drumlins. I read drumlins are common in New York State and Wisconsin, Poland, Estonia, Finland, and Patagonia. The formation of brand new drumlins was observed for the first time in Antarctica not too long ago. (See BBC news: news.bbc.co.uk/go/rss/-/1/hi/sci/tech/6295395.stm)

Recently Kevin Myers alighted on drumlins in his book Watching the Door, a memoir of his time as a journalist in Belfast during the Troubles. Rather than the above explanation he reckons the word comes from droim, Irish for ridge and lin from the English ling meaning; being like. This sets him thinking of the drumlin landscape as being a place where Irish and English meet, or rather clash. Myers associates the drumlin landscape with an unconquerability, a unsmoothable division between Anglo and Irish. The basket of eggs topography is a landscape for harrying, hiding, smuggling, and struggling. A landscape for guerrilla wars that can never be won but never quite lost and a good base for the myth-writing that support them: “this miserable hallucination of the drumlin, whose myths conjured poison from the soil …”

Myers uses the drumlins as a stand in for the Border. When his time as a journalist in Belfast is over he goes south to Dublin and gets “clear of the drumlins and their malignity.”

Estyn Evans, Geographer and founder of Queen's school of Geography, used to wax lyrical about the drumlins. He used them to highlight the diversity of Ireland’s land and people. He suggested the landscape of valleys and shadows the drumlins created is bonded to a local culture. A place of “limited vision and imagination. I always like to contrast that kind of hidden landscape [ ... ] with the open naked bogs and hills which are naturally areas of vision and imagination.”

I do not agree with Evans’ categorisations although I cannot help but think there is much potency in a landscape to shape culture. Evan’s falls in with the old Western/Instinctual/Catholic and the Eastern/Acquired/Protestant duality. It is hard to tell who is more hard-done by these stereotypes. But nonetheless Evans’ view of the drumlins is more useful. And after decades of conflict we need useful now. Myers uses the drumlins as a simple symbol for oppressive times and as backdrop to his tall tales. Evans, as a geographer, uses the drumlins as markers of a regionally diverse Ireland. A land of as many peoples are there are terrains. This is a point worth making and showing us the northern drumlins is his way of doing it.