Byzantine iPad?

The excavations at Yenikapi, the location of the old harbor of Byzantium, have continued to amaze archaeologists for years now with the fantastic preservation of organic materials at the site, from the particularly poorly known periods of the Late Roman and Early Byzantine Empires. I’ve actually written previously on this blog about some of the work Cornell University’s Dedrochronology Lab has done with all the wood from ships and piers that have come out of this amazing archaeology site! But today, we’ve got something really different!

Tablet bilgisayarin atasi kabul edilen not defteri

This particular artifact has made a bit of a stir, first because its genuinely very very cool, and second because some archaeologists or journalists have decided to pithily compare it to the modern laptop. This kind of comparison isn’t all that unusual in archaeology today – its a technique pioneered by Prof. Ian Hodder of Stanford who referred to trade of Neolithic obsidian blades at Çatalhöyük as being like the invention of the credit card. (Bonus: In the comments, tell us what you think about this sort of aggrandizing behavior in archaeology!)

But before you scoff at this seemingly ridiculous comparison between a some strange pieces of wood and our modern marvels of aluminum, silicon, and plastic, step back and you might realize that it could actually be an interesting and useful analogy. This artifact is a more complex version of an object we know from other, earlier, excavations of ships. In fact one of these, a diptych, was found on the Bronze Age (that’s 2000 years before this one!) shipwreck at Uluburun. The pages of diptychs or triptychs (depending on whether they had two or three pages), consisted of wooden frames and backs into which wax was poured. Once the wax hardened, you had a book that you could take notes in with a wooden stylus, erase, and reuse, to record information you only needed for awhile, or to save until you had a chance to write it down properly somewhere. No fiddling about with ink or charcoal or paper, which one can imagine onboard ship was particularly useful.

This particular notebook is even more interesting than others we know of though – in addition to multiple pages, rather than just two or three, this one has a sliding compartment in which weights would have been stored, which would have been used for calculating purchases and weighing coins! So, notes, measuring, and computing, all in one small convenient package that you can hold in one hand! Its practically an iPad! Okay, maybe that’s stretching it a bit…’

Image Credit and News Source: Hurriyet Daily News

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Salt is bad, Liminality, and the Harbour at Alexandria

I seem to be on a harbour kick this week, but they keep cropping up in my news feeds so they are what I’ve been thinking about. Or as Levi-Strauss would have said, they’re “good to think with.” Because harbours are interesting places. It’s where the water meets the land, a threshold where ships of war and trade dock, where people from different places interact. One of my professors, Dr. Christopher Monroe, a Senior Lecturer at Cornell University, has recently been spending a lot of time thinking about the liminality of harbors and how that liminality can be approached using nautical/maritime/underwater archaeology. His enthusiasm is infectious, and I too have found myself seeing liminality everywhere.

There was a lot of news today on a subject directly related to this: the lifting of a 9-ton red granite slab from the its resting place on the seabed in the harbour at Alexandria. This particular massive block of stone is believed to have come from a temple built by Cleopatra VII (that would be the Cleopatra, the one who ousted her brother, fooled around with Caesar, and then backed the wrong horse with Marc Antony). Archaeological work has been going on in the harbour since 1994, but nothing has been removed from the water since 2002. This was for good reason: the Egyptian archaeological authorities simply didn’t have the resources to deal with the conservation of artifacts and architecture from an underwater excavation.

The BBC reported that it was because the removal might damage them, which is only sort of true. The actual process of removal, like any excavation, is unlikely to damage the items if done with care. It’s really what happens afterwards thats the problem. The Associated Press article correctly reports that the salt in the seawater is the cause for concern, but in an impressive misunderstanding of science, they claim that when the object is in the water the salt acts as a preservative. This really isn’t true. Salt actually has very little effect on most types of material while they are submerged in seawater, except for the indirect effect it has on the how much oxygen there is present in said seawater. An ancient ship sunk in freshwater can be just as well-preserved as one in salt water. But, likewise, the salt doesn’t do any harm.

Think about it: when you dissolve a spoonful of salt in a glass of water it “dissolves,” and vanishes. What’s really happening is that “salt”, i.e. sodium chloride, is what in chemistry is also called a “salt,” which is an ionic compound resulting from a neutralization reaction of acids and bases. In the case of Sodium Chloride (NaCl), or table salt, one atom of sodium, with a single positive charge (Na+), is neutralized by a single atom of chlorine, with a single negative charge (Cl-). When in solution (i.e. dissolved in water), the sodium and chlorine ions interact with the water (H2O) which actually exists in a partially ionized state itself (H+ and OH-). Basically, all the ions are floating around together, neutralized, stable, and happy. But when the water is removed, say for example by evaporation, the sodium and chlorine ions are left on their own, and in a panicked effort to stabilize themselves they link up, and they happen to link up in an orderly fashion, which is what produces crystals. This orderly crystalline structure that the ions aline themselves in is sort of like an open-lattice, so it also takes up way more room in crystalline form than it did when it was just a bunch of little individual ions.

This whole process isn’t so much of a problem when it happens on the surface of something. When you go to the beach and go swimming and then fall asleep in the sun, you just wake up with a thin layer of salt crystals all over your body, which you can just brush off with a towel. But when an object is porous and all the water evaporates from inside it, the salt will crystallize wherever it happens to be and that includes inside the porous object. And in reality, just about everything is porous if you leave it sitting in water for several hundred years. Even granite. And when those ions form up into their surprisingly strong lattice crystalline structure, where they take up way more room than they used to, the resultant salt crystals will push on and possibly even break apart the material that they’re forming inside. Even granite.

So what this means is that if you were to pull an object out of the sea that’s been saturated with saltwater, say a giant slab from the pylon of Cleopatra VII, and then just let it sit in the sun to dry out, little salt crystals would form all over the inside of the stone, and it could quite possibly crumble into a heap of dust. This would be why the Egyptian government didn’t want people pulling things out of the harbour at Alexandria. Fortunately there is a reasonably simple solution to this problem. If you take the object that has been saturated in seawater and soak it for several months in rotating baths of fresh water, the salt can be leached out of the object until it is sufficiently desalinated and safe to allow it to dry. Such will be the fate of this carved granite block, which took three days to drag to safety away from the shipping lanes and close enough to shore for a crane to pull it out of the sea, only to be put back into a giant tank of water.

So, what does this have to do with liminality? The word “liminal” comes from the Latin, limen, meaning “threshold” or “doorway”, and in the early 20th century entered anthropological discourse in Arnold Van Gennep’s seminal work, Les rites de passages. In this work liminality is presented as the second of the three stages a person passes through in a rite of passage: Preliminary (separation), Liminal (transition), and Postliminary (reintegration). The liminal phase is characterized by ambiguity and paradox, during which the participant exists simultaneously to both the preliminary and postliminary states and to neither.

This is a great metaphor to consider a harbour with. A harbour is the physical embodiment of a doorway or threshold for a city or civilization. The ships and people who pass through it belong both to their home ports and to those that they visit, while also having no home at all. The harbour is of the sea and of the land, but is also its own thing, and the harbour at Alexandria is no exception.

Berth for the world’s great fleets, former site of mighty palaces and temples, crossroads of the Mediterranean, center of trade, war, and knowledge, the harbour has seen history pass, and it now holds in its depths the remains of that history, the detritus of history trapped in its own liminal state, having both passed out of time and memory, but also preserved, not truly allowed to fade. And this one block (9 tons of carved red granite), of this temple (to the goddess Isis), built by this queen (Cleopatra, perhaps history’s most famous), has finally escaped its liminal state in the murky depths of the harbour…

…only to enter another liminal state, stuck in a tank of fresh water in a conservation lab, thanks to being submerged in salt water for 2000 years. Thankfully, this one should be a lot briefer.

Links:
BBC News – Egypt lifts huge ‘Cleopatra temple’ block from sea
Monument lifted from Cleopatra’s underwater city

Stinky Wood, or the Byzantine Harbour at Yenikapi

Cornell University has a world-famous dendrochronology lab. Well, world-famous to people who keep tabs on things like dendrochronology labs. My advisor, Prof. Sturt Manning, is the director of the lab and after I took his dendro course at Cornell, I spent a semester working in the lab for some extra money. One of these days I’m sure I’ll write a post about all of the very cool things that you can do with dendro. Because they are VERY cool. But this post is going to be about dendro samples. Specifically the samples from a site known to the Cornell dendro lab as YNK, or Yenikapi.

The problem with being a grunt in the dendro lab is that you get to work on the material that no one else wants to. When I worked in the lab the post-docs and full-time researchers all had their own personal projects, and the students in the dendro course were given some choice in what kind of material to work on for their final projects. This left for the techs the samples that were hard to work with, boring (there are only so many cedar cores you can read from Cyprus before you want to gouge your eyes out), or… the wood from Yenikapi.

For the past three years the lab at Cornell has been flooded with samples from Yenikapi. The lab techs don’t get told too much about the samples that they are working on. Its just another piece of wood that has to be prepped appropriately, stuck underneath a microscope, and have each of its rings read and recorded in the computer to the precision of 1/100,000th of a meter. That’s 100ths of a millimeter. But even when we didn’t know what Yenikapi meant, me knew what having to work on Yenikapi meant.

See, there are four main kinds of wood that come into a dendro lab. First are your samples from living or recently deceased trees. Theses are cores or slices, usually in really good condition, that just need to be mounted and then sanded to a beautiful mirror finish before they can be read. Second are cores or slices taken from older decease trees… these might come from the wood used in a historical building or from an artifact like a piece of furniture, a coffin, or even the wood panel backing to a Rembrandt. Likewise these must be mounted and sanded, but often the wood isn’t in as good condition and the samples can be smaller and more fragile. The third and fourth categories of samples are the types found in archaeological or paleontological contexts, as they are ancient wood that has been somehow preserved. The third category is burnt wood, or charcoal, as once the wood has been reduced to carbon it usually doesn’t decay any further, unless it is damaged by water or impact (microscopic flakes of burnt wood can’t have the rings read!). The charcoal is wrapped with cotton string and masking tape to stabilize it, and then a clean surface is prepared for reading with a razor blade. The fourth and final category of sample is wet wood. Yenikapi is wet wood.

When wood or other organic material is submersed in water it doesn’t decay the same way it would on land, as there is no oxygen present. However, wood usually isn’t submersed in perfectly clear distilled water, and the salt, other chemicals, and biological agents found in the water have a definite effect. This is why sunken ships and old piers last so long, even for thousands of years, but not forever. The wood becomes dark and discolored, the structure of the wood becomes completely saturated and spongy, and finally it does eventually disintegrate. It can also be pretty gross. To get a smooth surface that allows the rings to be read, the sharpest razor blades must be used, and even they can often only make two or three cuts before they become too dull, and instead of shaving the surface of the delicate sample, you smoosh it into unrecognizable goo or fluff it into a cashmere sweater. The frustration of prepping wet wood must be experienced to be truly appreciated, and takes a remarkable amount of patience, which I really didn’t possess. There was lots of swearing involved. Thank god they put that lab in the basement and the prep room behind its own heavy door.

Additionally, wet wood samples aren’t sent into the lab submersed in water as they were found, as it simply isn’t practical. Instead the wood sample is tagged, and while still dripping wet its sealed in a Zip-Lock baggie. Now ideally, the air is removed from the bag, but its nearly impossible to get it all out, and sometimes the air removal step is skipped entirely. So, take organic material, and stick it in a moist environment in the presence of oxygen, and what do you get? Mold! Mildew! Fungi! Louis Pasteur would be horrified. Not to mention all the weird little insects from the water and the wood which just keep on merrily reproducing! I have seen wet wood under a microscope that looked like the surface of some alien planet, covered in a dense forest of bizzare trees and giant toadstools. It even has its own unique lifeforms, as bright orange and silver and even translucent insects scurry through the spongy remains of the wood.

Yuck.

But really, its the smell that gets to you. Because the wood from Yenikapi is oak that was submerged in the filthy stinking harbour of Istanbul back when it was still Constantinople. Some of it came from the hulls of sunken ships and some from the pilings of the Byzantine piers, but eventually this part of the harbour was filled in, most likely with garbage and household refuse and lord knows what else (the same way Manhattan was expanded in the 18th and 19th centuries), and after sitting down there, muddy and foul for over a thousand years, the whole area gets ripped up during the construction of a new subway system, and the archaeologists swarm in to do their thing.

And several hundred pieces of wood with the consistency of an overcooked souffle and a scent that falls somewhere between a high school linebacker’s jock strap and a rodent that’s been dead for a week, with notes of decaying seaweed, sewage, and the acrid tang of seawater, end up half a world away in the Cornell dendro lab.

The archaeological work on the site has steadily increased since the site’s discovery in 2004, as the Turkish government really wants to move forward with construction, and as a result more and more Yenikapi samples have flooded the lab each year. There was so much of it this year, that I heard its all the students or the lab techs get to work on. For once, I am thankful for my thesis.

Links:
CNN article about the construction at Yenikapi
Cornell Tree-Ring Laboratory
excellent Saudia Aramco World article about the archaeology