Unreinforced concrete domes. We have all seen objects made out of concrete. Small ones, big ones, here, there, and everywhere. Concrete is really useful, as it is strong and can be poured into almost any shape. So how old is the largest unreinforced concrete dome? A century? Hardly. Two centuries? They were using concrete in the 1800's? They were, but we're going back farther than that. Add a zero, almost.

I give you the roof of the Pantheon in Rome.

It was finished in 128 AD, nearly two thousand years ago, and it is still the largest unreinforced concrete dome. And it is beautiful. That opening at the apex--the oculus--is just as impressive today as it was then. And it's clever, removing the apex of the dome removed a good deal of stress from the structure. And those pretty recessed panels--coffers--aren't just ornament as they reduce the weight of the structure.

Now for some qualifications. I am not an architect nor am I an architectural historian, so I could have some details wrong. I can't find any information on reinforced concrete domes, but maybe that is why the Pantheon's dome is still the largest of its kind. I know that expertise in the use of concrete declined after Rome 'fell,' but I do not know how much or how fast.

It is an incredibly beautiful building, though.

A closeup of the roof's exterior

An overhead shot, apologies for the poor resolution

A photo featuring the oculus

How pretty is that?

Here's a pretty prosaic one. Garum.

We know the Romans loved the stuff and used it with everything, yet every single time I've seen a documentary on Roman cooking or an experimental archaeologist who's tried to reproduce it, they've ended up making something that's smelled and tasted absolutely horrid.

Now obviously tastes are different from culture to culture and from time to time, but I have a hard time believing that things have changed that much. In fact, as the wonderful blog Pass the Garum has shown, Roman cuisine wasn't that far outside the taste buds of a modern person.

So why is it that nobody can seem to reproduce a decent tasting garum? Wrong recipe? Not following directions? Missing key ingredients? Producers want to end up with a bad tasting failure because that's better tv?

The only one I've seen who's come close is Heston Blumenthal in his Roman Feast and he kind of cheats by using a vacuum pump instead of waiting three months like the recipe supposedly calls for.

So what's the deal with garum?

So in Judaism you can't talk about lost arts without talking about tekhelet. It's a blue dye used in various ritual objects. Besides things in the Temple, it was used in the tzitzit, a sort of fringe that goes on a ritual garment, the tallit (I'm going to avoid rambling off-topic about this--if you're curious, ask). It was lost in antiquity. After the Temple was destroyed and most of the community was exiled, a lot of the ritual infastructure for things like that died off. While the dye persisted for a few centuries after, it eventually was lost in the centuries immediately following the Talmud. However, Jewish texts give several important facts about it:

1. The dye comes from a Mediterranean snail

• The snail has a shell
• The snail is fish-like
• The snail is rare
• Its color is like indigo, though it is not made from it
• It is expensive

Because of its relevance in Judaism, people have tried to identify it. An incorrect one was the cuttlefish--it turns out the dye made from it has nothing to do with the cuttlefish, it's actually the Prussian Blue artificial dye, using the cuttlefish as a source of organic material. And the important bit about the dye is the animal it comes from.

However, this happily falls into the third category! Someone eventually tried a snail that fit the bill, the hexaplex trunculus. And more importantly, archeologists have found evidence of that snail used in Near-Eastern dye production. It's actually the same animal that made the ancient royal purple, but with a slightly different process. Importantly, it's known to have been used by other Canaanite groups, including the Phoenicians. And based of a bit of dyed fabric, it seems that tekhelet was a dark, almost purple, blue color. After all, it's said to be the color of indigo.

Whether or not people should use tzitzit dyed with this is an interesting question of Jewish law. But either way you can buy them now. Which is pretty cool.

Can we talk about obscure arts that aren't quite lost? Chant hand-signalling is part of Jewish liturgy that's in grave danger in most communities.

Not so much lost as ignored by the people who adopted maize post-Columbus without also adopting millenia of indigenous knowledge of the crop, but nixtamalization seems to fit this bill. It's actually a fairly simple process: after harvesting maize, you soak the kernels in an alkaline solution for a bit, then rinse and process into what even you want (like masa, for delicious delicious tamales, which would probably go good with some garum). The reason for this is that an essential nutrient in maize, niacin (Vitamin B3), is otherwise not readily bio-available. In diets heavily dependent on maize, this nutrient deficiency leads to pellegra, a disease notable for its "4 D's": diarrhea, dermatitis, dementia, and death. Basically, after shitting your guts out, your skin crusts over, you go insane (sometimes violently), and then you die.

Obviously, Native Americans had figured out the trick to release the niacin, but this knowledge did not travel with maize kernels back to Europe, or anywhere else maize was integrated as a staple crop. In time, the ready abundance of maize turned out to be a bit of a curse, as poor people in Europe, the U.S., and elsewhere came to rely on maize-heavy diets, leading to an epidemic of pellgra.

So how long did it take for the "lost" art of nixtamalization (which has never stopped being practiced in Mesoamerica) to be "rediscovered?" Well the connection between maize and pellegra only took a few centuries. It wasn't until an American physician, Joseph Goldberger, took on the problem in THE EARLY 20th CENTURY in a serious attempt to discover the root cause of pellegra that the matter was settled. The NIH has a great summary, but I've also collected links to, and quotes from, some of the most important papers Goldberger published on the topic over at /r/historyofmedicine.

Pellegra was only recognized as a distinct condition in the 18th Century, which cases being almost exclusively confined to the rural poor, who we all know were destined to suffer in life anyways, the proof being that they were poor. There's an excellent paper giving on overview of early efforts to identify the cause of the disease here, but the reality is that it was Goldberger's work that closed the debate by showing that:

• People in close association with "pellagrins" but living in different conditions did not catch the disease (i.e. prisoners vs. guards)

• Pellegra could be induced by feeding someone a poor, maize-dependent diet (prisoners were also used for this, yay medical ethics in the past!)

• Injecting yourself with pellgrin's blood and exposing yourself to their, um, bodily materials, could not produce the disease

• Changes in diet could prevent/reverse the disease, especially the use of brewer's yeast (delicious delicious marmite)

Finally in 1937 Elvehjem et al. showed that niacin could prevent canine "black tongue" (essentially pellagra for dogs) and thus vitamin fortification of maize began. Whither nixtamalization in all this? Nowhere to be found. It wouldn't be until 1951 when Laguna and Carpenter^1 noted that:

In Mexico there is very little primary pellagra, although there is a high per capita consumption of corn by some sections of the population, which also eat only small quantities of "animal protein" foods. One difference, among others, between the Mexican conditions and those pertaining to pellagra areas is that the corn in Mexico is eaten in the form of "tortillas" prepared in the first stage by cooking the whole corn in lime water.

^(1 Laguna & Carpenter 1951 Raw Versus Processed Corn in Niacin-Deficient Diets. J Nutrition, 45[1])

I just made a rather long and lengthy post about this the other day: while we know of numerous other incendiary devices used throughout antiquity and the Middle Ages, we don't actually know the recipe for "Greek Fire." (The version used by the Byzantines, not the aforementioned other varieties, which were collectively lumped together under the name "Greek Fire" by the Crusaders.)

That isn't to say that we don't have theories, though. Numerous attempts have been made to figure out what exactly made the Byzantine weapon unique, in both it's composition and in its delivery system -- I described them both in depth in this post here. There is actually a recipe published by one Marcus the Greek in the 12th century, but is unclear if it is the same as the Byzantine version.

In any case, while we have some pretty good ideas, the secret of Greek fire is definitely a "lost art."

Edit: For those of you with access to JSTOR, this article is a pretty good read on the topic.

Raised bed Agriculture in the Andes. By raising the beds and surrounding them with water canals it keeps the soil from changing temperature quickly. Which allowed a longer growing season and also provided a habitat for fish frogs and birds which could also be harvested.

http://www.sas.upenn.edu/~cerickso/articles/Exped.pdf

I recall reading that nobody has been able to replicate the celadon glaze that was a trademark of Goryo-era Korean pottery- is that true? I've always been particularly taken with the handiwork of the period.

A much more recent example is in the techniques used to build the Saturn V. There are blueprints still available, but the jigs and techniques were not as carefully recorded. How do you set about building a 6.6m ring on a lathe? You would have to build a new lathe first.

Is Damascus steel technology really lost? Or has it been rediscovered/reconstructed?

Historians, does Terra Preta qualify?