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Erin McCarthy

Spending Time Among the Bones of Paris's Catacombs

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Erin McCarthy

In Paris, what’s beneath the sidewalks is as exciting as the monuments that tower above them. The underground is a labyrinth of canals, crypts, vaults, reservoirs, and hundreds of miles of tunnels ripe for exploration. Some people who roam beneath the city are doing it illegally to repair neglected treasures, throw parties, or paint murals, but there are legal ways to explore the canals and crypts, too.

For a fee, access is granted to an approved section of les égouts—or the sewers—which Victor Hugo called "the conscience of the city" in Les Miserables. (To accurately write about Jean Valjean's trip through the sewers, Hugo called on help from his friend, sewer inspector Emmanuel Bruneseau.) Visitors with more macabre interests, however, can descend 65 feet underground, below the metro and the sewers, to walk amongst the bones of the dead in the famous les Carrieres de Paris—also known as the Catacombs.

Arrête, c'est ici l'empire de la mort

Forty-five million years ago, a tropical sea covered the area that would become Paris. Over time, the sediment on the seabed became formations of limestone, which the Romans would mine when Paris was known as Roman Lutetia. Open quarry pits gave way to nearly 187 miles of underground tunnels, which provided the stone that built the Louvre and Notre Dame.

Eventually, the quarries were abandoned. But in the 18th century, they became the best solution to Paris’s growing public health problem.  

In the late 1700s, the mass graves at cemeteries like Saints-Innocents in Paris’s Les Halles district were overcrowded with bodies. Improper disposal of corpses led to unsanitary conditions that contributed to the spread of disease.

To save the living, authorities shut down Saint-Innocents and, in April 1786, began relocating the remains buried in the cemetery to the Tombe-Issoire quarries, which had been blessed and consecrated for the purpose. Transferring the bones from the Saints-Innocents Cemetery—the largest in Paris—took two years. Between 1787 and 1814, bones were transferred from other Parisian cemeteries; the final transfer of bones took place in 1859.

A number of notable people buried in those cemeteries likely had their bones transferred to the Catacombs. The list includes writers Jean de La Fontaine (Fables) and Charles Perrault (known for fairy tales like Little Red Riding Hood, Cinderella, and Puss in Boots), painter Simon Vouet, and architect Salomon de Brosse (who designed the city's Luxembourg Palace). During the Revolution, people were buried directly in the Catacombs. Guillotine victims ended up there, too, including the likes of Maximilien Robespierre, Antoine Lavoisier, and Georges Danton, all beheaded in 1794.

The Catacombs hold the artfully arranged remains of 6 to 7 million Parisians. Above the entrance to the ossuary, carved into a stone, are the words “Arrête, c'est ici l'empire de la mort.” Stop, this is the empire of the dead.

Taking a Tour

The Catacombs opened to the public in the early 19th century. Visitors enter on Avenue Rene Coty and descend 130 steps to the former mines, where a truly spooky, interesting journey awaits.

The walls of the narrow corridors that lead to the ossuary are marked with the names of the streets and historical information. Visitors will pass through "The Workshop," an area of the former quarry featuring stone pillars that support its ceilings.  

Next is the Port-Mahon corridor, which features sculptures created by a quarryman named Decure. The corridor is named for the sculpture of the Port-Mahon, above; Decure, who had fought in the armies of Louis XV, may have been held captive at the fortress by the English. Visitors will also pass the Quarryman's footbath (below), which was uncovered by workers and used for mixing cement.

And then comes the ossuary. The sheer amount of bones in the former quarries is staggering. Though the bones inside are artfully arranged now, it wasn't always that way; at first, they were simply thrown inside. But around 1810, Hericart de Thury, the inspector of the quarries, had the bones organized. (Behind those facades, the rest of the bodies were piled in heaps stretching back to the cavern's walls.)

In addition to these artfully arranged bones, visitors can see a number of interesting things, including commemorative plaques, a sepulchral lamp used by quarrymen to make air circulate through the corridors, a cross and an altar, a spring called Fontain de la Samaritaine, and a single tombstone (it belongs to Françoise Gellain). Two features of the ossuary disguise structural reinforcements: Gilbert's Tomb, which features a verse from the poet (who is buried elsewhere), and a barrel-shaped display of skulls and shinbones in the Crypt of the Passions. (On April 2, 1897, two workers let in scientists, scholars, and artists for a middle-of-the-night, very secret concert held in the crypt. When their identities were discovered, the workers were fired.)

Workers are scattered throughout the Catacombs to answer questions, but mostly, visitors walk alone or with companions through the dimly lit, damp, nearly-silent space. The rules when wandering the catacombs are simple: Respect the final resting place of these Parisians. Look, but don't touch. Don't leave your mark at all, especially with graffiti. It might be tempting to snag yourself a souvenir from this most unique of attractions, but bags are searched for bones at the exit. If you're still looking for something to commemorate your visit, there's a gift shop just across the street.

All photos by the author.

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iStock // Ekaterina Minaeva
technology
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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iStock
Animals
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Scientists Think They Know How Whales Got So Big
May 24, 2017
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iStock

It can be difficult to understand how enormous the blue whale—the largest animal to ever exist—really is. The mammal can measure up to 105 feet long, have a tongue that can weigh as much as an elephant, and have a massive, golf cart–sized heart powering a 200-ton frame. But while the blue whale might currently be the Andre the Giant of the sea, it wasn’t always so imposing.

For the majority of the 30 million years that baleen whales (the blue whale is one) have occupied the Earth, the mammals usually topped off at roughly 30 feet in length. It wasn’t until about 3 million years ago that the clade of whales experienced an evolutionary growth spurt, tripling in size. And scientists haven’t had any concrete idea why, Wired reports.

A study published in the journal Proceedings of the Royal Society B might help change that. Researchers examined fossil records and studied phylogenetic models (evolutionary relationships) among baleen whales, and found some evidence that climate change may have been the catalyst for turning the large animals into behemoths.

As the ice ages wore on and oceans were receiving nutrient-rich runoff, the whales encountered an increasing number of krill—the small, shrimp-like creatures that provided a food source—resulting from upwelling waters. The more they ate, the more they grew, and their bodies adapted over time. Their mouths grew larger and their fat stores increased, helping them to fuel longer migrations to additional food-enriched areas. Today blue whales eat up to four tons of krill every day.

If climate change set the ancestors of the blue whale on the path to its enormous size today, the study invites the question of what it might do to them in the future. Changes in ocean currents or temperature could alter the amount of available nutrients to whales, cutting off their food supply. With demand for whale oil in the 1900s having already dented their numbers, scientists are hoping that further shifts in their oceanic ecosystem won’t relegate them to history.

[h/t Wired]

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