Friday, July 28, 2006

Dendritic



Before I left on holiday, I read the recent post At One Remove about Hele-Shaw cells. The sculptor Richard Aumonier has a photograph of himself blowing air into a Hele-Shaw cell (glycerin between two sheets of perspex) and creating a snowflake-like pattern. The dendritic branching of the pattern appears to become exponentially more frequent the further in distance the spreading, unstable air front is from the central blow hole. It's an example of what specialists call 'viscous fingering'. Richard has used the technique to create a series of rather beautiful prints.

The word 'dendritic' comes from the ancient Greek word for 'tree'. Dendritic things branch in the same ways that trees branch. If you feel in need of some tree refreshment, have a look at Via Negative's recent Festival of the Trees. It includes a piece of my writing and is a great community blogging effort summoned together by Dave Bonta. Of course, with trees, both branches and roots are dendritic and form a symmetrical system linked by the trunk.

Many other natural phenomenon are also dendritic: The forking of lightening as it reaches from the clouds towards the ground; the gathering of stream tributaries in a river and the branching of its distributaries when it reaches the sea. The river system is symmetrical, one end of it gathering water, the other end dispersing it. Minerals may form dendritic crystal structures and in most metals, the process of solidification from a molten state occurs through the formation of dendritic structures. Rapidly cooling water forms dendritic ice crystals and snowflakes are tiny dendritic structures.

Sometimes one dendritic effect can be mistaken for another. Here is the view of one planetologist who thinks that recently identified sinuous channels on Mars are not the result of fluid movement but rather the evidence of huge lightening strikes which have produced soldered, branching structures on the planet surface. Such structures are formed on earth when lightning grounds itself in desert sand. The molten sand streaks may resemble the roots of a tree and are termed fulgurites.

While I was away on holiday, I noticed that the stones in the crazy paving around our rented holiday house had iron oxide (brown) and managanese oxide (black) dendritic structures, seeded off cracks in the thin limestone slabs. I imagine the slabs may be Lower Jurassic in age such as those from Solnhofen in Germany which show similar structures. The stones were probably sourced locally in the Dordogne region however. I took some photographs like the one at the top of the page which you can view here. These dendrites look like landscapes. I have the feeling that the manganese dendrites look slightly different from the iron dendrites, being slightly more spindly, chaotic and less formal. Perhaps they differ in form according to their crystal chemistry. One of the manganesse examples I photographed (the second photo) seems to show Mandelbrot type embayments.

Similar dendritic patterns can occur in agate, but are three-dimensional in character. The resulting rock is called moss agate (so named for its plant-like appearance) and also Mocha stone due to the fact the it was brought to Britain from traders departing from the port of this name in Yemen. Today, most of the Mocha stones are obtained from India, where they are found among the agate-pebbles resulting from the disintegration of the trap rocks of the Deccan.

Mocha stones gave their name to Mocha ware which is a style of pottery invented in Staffordshire in the 1780s. Mocha ware has slip decoration based on reproducing the natural dendritic mineral patterns of Mocha agates and dendritic limestones. The original recipe involves touching a water-based mixture of boiled tobacco and iron oxide onto the wet surface of the pot. The acidic "tea" reacts with the alkaline slip and the dendrites grow quickly from the point of contact. For more information and a lot of fascinating and beautiful nonlinear physics see here.

The site I've linked to says that: "The dendritic pattern of mocha ware is a result of a dynamic process in which the contact line between the two liquids, tea and slip, becomes unstable. The surface tension of the tea is less than that of the slip. The instability is probably driven by a combination of capillary and Marangoni (surface tension gradient) stresses, coupled somehow to the acid/base chemical reaction."

To return to where we started, I should imagine that when Richard Aumonier produced his Hele-Shaw cell prints, he reflected that the air he was blowing into the cell came from his own lungs which themselves have a branching structure very similar to that produced inside the cell. Perhaps that is how he came to arrange some of the prints as paired lung shapes.

The formation of dendrites seems to evolve from instabilities. They reflect gatherings, transport and dispersions of energy. Perhaps the universe, resulting from a cosmic instability, is itself dendritic.

Certainly, I think that most peoples' lives are dendritic. We begin from nothing, as a mass of little gathering streams: information, learnings coming from all over, pulling them into ourselves, gathering them around us, weaving them together. Such is nursery, school and university. All those subjects which we had to learn and yet now use so little of. Too bad. We take the 5% we do remember into ourselves to make us stronger.

The more streams we gather, the stronger we shall be as we surge onwards, become constant, find a plateau, a direction, a purpose. Then, everything we have learnt comes together and makes us good at what we do. We do not need to search around for clues. Every response comes powerfully from within us.

Then finally, we can't cope with it all. We start to give things up. One by one we let fall away skills, memories, good routines. We are aging, failing, coming apart. Freely, we give away advice, wisdom, all that we have learnt, all that we have carried with us along the way. Now it is a burden. Fragile, moss-like, we are dispersed, dissipated, dying away.

Wednesday, July 26, 2006

Portrait de mon Papa



My youngest, who is four, drew this picture of me for "la fete des Papas" in June.
Aptly, since her Papa is a sedimentologist, it is on sandpaper.

On the back there is a poem in French:

Un papa rapluie
Qui me fait un abri
Quand j'ai peur de la nuit
un papa ratonnerre
Je ne sais pas quoi faire
Quand il est en colere
Un papa rasol
Avec qui je m'envole
Quand il rigole
Un papa tout court
Que je fete en ce jour
Avec tout mon amour.

It's by Pierre Ruaud.

Sunday, July 16, 2006

Woodchip Wallpaper and the Meaning of Cave Art



When I was a youngster, my family moved into a house that had woodchip wallpaper in the downstairs loo. Woodchip wallpaper is a kind of textured paper which has small flakes of wood incorporated into it during its fabrication. Each flake is a small, rough-edged and individual creation of different shape and size. Sometimes a number of flakes will aggregate together to form more complex clusters. The individual woodchips or the small clusters, however, form discrete elements in the wallpaper having little interaction with each other, a bit like falling snowflakes.

Every time I went to the loo, I would sit gazing at a patch of this white-painted woodchip wallpaper. As I gazed, certain chips or clusters of chips would begin to be reminiscent of a face, an object, an element of nature, a tree, a flower, a fence, and the more I looked, the more it came to seem like that thing it resembled, and the less it came to seem like anything else. Finally, the object would require to be named: it would be "The Gun" or "The Farmhouse", "The Robber" or "The Skull".

The next time I returned to the loo, the same objects would still be there. I would have no problem remembering them now, and what is more, the objects would be connected by an invisible line which marked out a narrative that had begun to develop between each one of the objects. The narrative was conjured up by the images and was driven by the individual elements as they were added. The invisible line connecting the objects grew steadily longer as I recognised new objects and perceived their place in the story. The story was certainly a slightly odd one, dreamlike in character, but it had its elements of drama as indicated by the titles of individual woodchips that I referred to earlier.

This story wasn't something I dreamt up one week and forgot about the next. Rather, it was one which sustained my imagination over months if not years. I never told anyone about my ongoing woodchip saga, but in fact, it was something I was quietly passionate about: both the daily repetition of the story and the addition of new elements into the extending "songline". (If you don't know what a songline is, then you must read Bruce Chatwin's book of the same title.)

I have been thinking about this after visiting the famous Font de Gaume cave in the Dordogne last week. This cave (pictured above) is now probably the best place for viewing original cave art in the Dordogne region. It is close to the town of Les Eyzies which houses France's national prehistory museum. The cave is not widely publicised and entry is limited to 200 people per day in order to keep the temperature inside low and the damage to the cave walls to a minimum.

I have also visited Lascaux II which is a perfect replica of part of the Lascaux cave, rightly renowned as the most beautiful and well preserved example of prehistoric cave art, certainly in France, if not in the world.

A common observation I took away from both these visits was of how sensitively the art had been overlaid onto the geomorphology of the cave interior. It is not an original observation and indeed it is something that is stressed by the guides that showed us around both Lascaux II and Font de Gaume.

The painters made no attempt to chisel flat the walls or to prepare a smooth surface on which to paint. Instead, they were intent on identifying the features already present in the rock and interpreting them through the addition of paint and fine chisel marks. The guide at Font de Gaume lifted his torch to create a shadow on a slight ridge in the rock, and it immediately became apparent that the shadow of the ridge defined the external form of the bison's head which was drawn there.

Like the indians in Papua New Guinea which I wrote about in a recent post who believed that the axe heads they chipped from the rock were already present in the rock, the prehistoric painters of reindeer, mammoth and bison in the Font de Gaume and Lascaux caves believed that the animals they were painting were also already there in the rock. All they had to do was identify their presence.

I feel certain that, as the painters identified the natural sculptural presence of these animals, a kind of narrative would have evolved for them similar to the kind of narrative I discovered through identifying real objects from ragged scraps of woodchip. Whether the narratives that were created might be readily interpretable to modern eyes I think is doubtful, but they would have been powerful enough to their creators and to anyone who was let in on the secret.

Good Things About France No. 7: The Bagatelle Rose Gardens



Many visitors to France are aware of the famous Chateau de Versailles gardens which are built on a grandiose scale and the smaller and more intimate water gardens of the painter Monet at Giverney. Perhaps less visitors are aware of the Bagatelle Rose Gardens which is part of the large expanse of parks and forest which make up the Bois de Boulogne situated to the west side of Paris and easily accessible by metro.

It is a fairly formal garden with a fabulous array of different roses whose overwhelming scents fill the summer air. The best time to visit is probably in June when the gardens have an annual International Rose Competition judged by the public.

There is a smart outdoor cafe just next to the garden where you can top up your radiator with Perrier water and if you still have energy left there is the Jardin d’Acclimatation next door which is the perfect outdoor amusement park for young children.

Friday, July 07, 2006

The Stone Axe



It is an incredible fact that at the end of the 20th Century, there were humans on one side of the earth sending people into space, while on the other side, humans existed whose highest technological achievement was the stone axe. The stone axe was an incredibly important technological development for mankind. Much more important than the spaceship. It allowed man to control his environment for the first time, chopping down trees and creating 'gardens' in the jungle.

Last weekend we went to see a special exhibition at the French National Archaeological Museum which is located in the chateau of St Germain-en-Laye, just outside Paris. The museum doesn't seem to get that many visitors and you can pass a very calm afternoon there, looking over the fabulous and well explained (if you speak French) exhibits.

The exhibition called 'Objects of Power in New Guinea' is based on a donation of material from two anthropologists who have worked in Papua New Guinea over a period of more than twenty years. The objects, and an accompanying film, document the importance of stone axes to some of the native peoples of this island.

A number of 'objects of power' are displayed which include the stone axes. The axe is an essential tool for the natives in their mode of life which is based on being able to clear patches of the dense rain forest and create 'gardens' where taro, maize and sweet potato are grown. As well as a practical item, non-utility 'axes' are used as an item of trade, dressed up in woven clothes like a woman. Consecrated axes cannot be touched without sacrificing a pig. The axe is a sign, symbolising the status of young men.

The men quarry the axes from a particular outcrop of glaucophane schist rock to which they have to hike for up to a week, an arduous and dangerous journey. They build a fire under the rock to make the stone expand and exfoliate. They then throw it into a nearby river so that it cracks and splits into pieces of suitable size. Another fire is used to reheat large pieces of stone before throwing them again into the river.

The natives believe that a deity was buried underneath the rock outcrop and that magic powers introduced the axes into this particular rock outcrop. They believe their work is simply to release the axes from the stone in which they are encased.

Once a suitable sized lump of rock has been found, the man begin knapping the edge of the stone to make it the right shape. They return to their village with up to a dozen pieces of rock each. These they model into perfect mirrored blades over the coming months, grinding the axes to a perfect edge on a sandstone block lubricated with water. The resulting axes are beautiful, their blades decorated by the patterns inside the rock. Green dye from plant leaves is used to give the axes a verdigris finish.

Here is the first technology of man. It gave him a hitherto unknown power over nature. He invested the rock from which the axe came with his own supernatural conception of the universe in which a greater power was giving him rights over the rest of nature. To that supernatural power, he began to sing praise in song and verse.

Wednesday, July 05, 2006

Football Crazies

I'm not a big fan of football. I've watched a few of the world cup matches. Some have been fair. Some have been foul. There have been a few perfect moments, like the goals in the last minutes of extra time of an otherwise boring Germany vs Italy match.

I had a fairly strong hunch France would win the match against Portugal tonight. I had to stop late at work so wasn't able to watch the game. It's a fairly horrible experience working late in 'the tower' when the weather's hot because they turn the air conditioning off at 7pm and it soon becomes more sweltering inside than it is outside.

When France scored their goal, many windows burst open in the tower block 100 yards away from the one I was in, and dozens of youths leant out from various flats, yelling and waving scarves. They seemed to be communicating their joy to other youths in another towerblock some distance away. I reflected on the fact that the only other occasion they would be likely to behave like that would be if their building caught fire.

I left the office before the match was over so as not to get too caught up in the aftermath celebrations. As my RER train sped towards the suburbs, suddenly we few passengers began to hear people in the stations we passed making a racket in any way they could: either beating a fist against a metal hoarding or simply shouting.

Cars started racing along the roads next to the train, beeping their horns, youths seated on the car window ledges and clinging to the roof or waving flags as the vehicles sped along.

By the time I reached my destination, roller-skaters and cyclists were taking to the streets. Cars were everywhere, hooting loudly, their passengers yelling their jubilation at any overworked fool who happened to be making his way home. By the time I arrived Chez Nous, I was relieved to be shutting my door on them all.

Sunday, July 02, 2006

Didactic by Joe Ross




It is comfortable
a chair under –
what stood.

That you can
not stand. Is
ground under
feet.


+++++++++++++


Joe Ross is the author of ten books of poetry, most recently, EQUATIONS = equals, Green Integer Press, 2004. He was the Literary Editor of the Washington Review, and co-founded both the In Your Ear reading series in Washington, D.C. and the Beyond the Page reading series in San Diego, CA. He received a National Endowment for the Arts Fellowship Award for his poetry in 1997. He presently resides in Paris.

This is part of a series of poems from invited poets. The first contributor was: Luke Heeley. Illustration by Jonathan Wonham.