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Karen Bleier/AFP/Getty Images

The Hidden Room Behind Mount Rushmore

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Karen Bleier/AFP/Getty Images

In the 14 years he spent planning, sculpting, and overseeing the completion of the Mount Rushmore monument, artist Gutzon Borglum harbored a deep concern. He worried that his creation—one that used a 400-foot-long by 500-foot-wide rock canvas to depict the faces of four influential U.S. presidents—would one day be shrouded in mystery.

After all, Borglum reasoned, what did we really know about Stonehenge? Or Egyptian pyramids? Civilizations could rise and fall while Rushmore stood, its origins getting more clouded with time.

To make sure people in the future knew the history of his project and the meaning behind it, Borglum announced an ambitious addition: a massive room situated just behind Abraham Lincoln’s hairline that would contain all the information anyone would ever need about the mountain. It would even house major historical artifacts like the Constitution and the Bill of Rights.

Borglum called it the Hall of Records. In 1938, he had workers begin blasting away with dynamite, carving what he wanted to be the most elaborate artist’s signature ever conceived.

The loud, brazen Borglum was born in 1867—at least, that’s the best information we’ve got. He enjoyed obfuscating his history, mixing and matching facts for his own amusement. A talented artist, Borglum thought he’d have a career in painting. When he saw his brother, Solon, making a reputation as a sculptor, sibling rivalry kicked in, and Borglum found he had even more to offer while working in clay.

After a modestly sized bust of Lincoln garnered Borglum national attention, he was invited to carve the faces of Confederate soldiers into Stone Mountain in Georgia. That work—which was never completed due to disagreements with local government—attracted the attention of Doane Robinson, South Dakota’s official state historian. Robinson told Borglum that a monument in the Black Hills of the state could be an excellent canvas for a work on a grand scale; in return, the state’s tourism statistics might flourish.

Borglum was intrigued. After scouting three mountains, he began to dwell on the possibilities present at Mount Rushmore. To draw national attention, he would focus on four presidents who had a tremendous impact on the country: Thomas Jefferson, Abraham Lincoln, George Washington, and Theodore Roosevelt. Each man would be depicted down to his waist. Alongside Washington would be a massive inscription detailing major events in U.S. history.

The actual carving began in 1927, with 30 men working at a time to blast rock with dynamite. The U.S. government subsidized most of the cost of labor, which would eventually amount to nearly $1 million.

As they doled out money, South Dakota and the federal backers were most concerned with Borglum etching the six-story tall faces into the east side of the mountain. But Borglum’s attention was diverted: as ambitious as the project was, he imagined something even greater. He wanted a room accessible to visitors that would have tablets explaining the work done, as well as busts of famous Americans and key documents like the Declaration of Independence. Those looking for admittance would climb an 800-foot-long staircase made from the blasted rock, then pass under a gold-plated eagle with a 38-foot wingspan.

The room began to take shape in 1938, when Borglum finally started blasting out an opening. A doorway 18 feet tall led to a room 75 feet long and 35 feet tall; red paint on the walls told workers where and how to extract the rock. Holes that housed the sticks of dynamite created a honeycomb effect.

Borglum’s ambition wasn’t shared by the government, which had a limited amount of funds to allocate and considered the room frivolous. South Dakota state senator Peter Norbeck wanted to help, and offered relief workers to assist in constructing the staircase. That way, federal funds wouldn’t have to be tapped.

Borglum, however, didn’t warm to the idea. He got a percentage of those federal funds, and using relief labor wouldn’t put any money in his pocket. He pushed the senator away in the belief he could grease the necessary wheels. 

Borglum’s self-confidence may have been his downfall. Governor William Bulow told him that finishing the faces was of the utmost priority, and that any ancillary work could be ignored until later. Any miner could blast a hole in the mountain—it took an artist to conceive of the actual sculpture.

Despite Borglum’s insistence he was in perfect health, Bulow’s urgency turned out to have merit. Borglum died in March 1941, leaving the Hall of Records unfinished.

With money and time at a premium, the government declared the monument more or less complete on Halloween 1941. Borglum’s ambition for a signature room would be costly, and no more work was done. It remains inaccessible to tourists.

His family wouldn’t drop the matter so easily. For decades, Borglum’s descendants petitioned the government to complete the room in honor of his work. Finally, in 1998, family members were able to assemble in the room and oversee a deposit of several porcelain tablets that explained the work done to the mountain. Lowered into a hole in the floor of the room, it was topped with a 1200 pound capstone. The Mount Rushmore National Memorial Society paid for the ceremony, which represented Borglum's posthumous completion of his landmark piece of art.

One of the tablets contains Borglum’s intention for both the mountain and the room inside of it:

"I want, somewhere in America, on or near the Rockies, the backbone of the Continent, so far removed from succeeding, selfish, coveting civilizations, a few feet of stone that bears witness, carries the likeness, the dates, a word or two of the great things we accomplished as a Nation, placed so high it won't pay to pull them down for lesser purposes.

Hence, let us place there, carved high, as close to heaven as we can, the words of our leaders, their faces, to show posterity what manner of men they were. Then breathe a prayer that these records will endure until the wind and rain alone shall wear them away."

All images courtesy of the U.S. National Park Service.

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iStock // Ekaterina Minaeva
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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Name the Author Based on the Character
May 23, 2017
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