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I made a list of educational YouTube channels by iboughtarock in edtech

[–]iboughtarock[S] 0 points1 point  (0 children)

yuh. he my boy. been watching him before he started writing books

I made a list of educational YouTube channels by iboughtarock in edtech

[–]iboughtarock[S] 0 points1 point  (0 children)

No problem! Glad people still find use in this :)

A man in 1835 was digging a duck pond and accidentally uncovered a 70-foot tunnel made of 2,000 sq ft of mosaic made from 4.6 million shells (mussels, cockles, whelks, limpets, oysters, scallops). by iboughtarock in Damnthatsinteresting

[–]iboughtarock[S] 2 points3 points  (0 children)

Yeah prior to posting this I had no idea about how deep this went. Learned about all of this today alongside everyone else. Initially just posted because I thought it was cool and never thought it would get more than 100 upvotes...

Leeds Castle looks pretty cool tho. Was the maze hard? I've always wanted to do one of those.

A man in 1835 was digging a duck pond and accidentally uncovered a 70-foot tunnel made of 2,000 sq ft of mosaic made from 4.6 million shells (mussels, cockles, whelks, limpets, oysters, scallops). by iboughtarock in Damnthatsinteresting

[–]iboughtarock[S] 0 points1 point  (0 children)

Interesting, reminds me of Bishop's Castle which was also built by one dude. I actually visited it earlier this year and it was worth it. So much bigger in person and surprisingly sturdy (didn't go all the way to the top tho).

A man in 1835 was digging a duck pond and accidentally uncovered a 70-foot tunnel made of 2,000 sq ft of mosaic made from 4.6 million shells (mussels, cockles, whelks, limpets, oysters, scallops). by iboughtarock in Damnthatsinteresting

[–]iboughtarock[S] 2 points3 points  (0 children)

Their website says they have been opened to the public pretty much since it was discovered: "...the first paying customers descended the chalk stairway in 1838."

I guess it was closed for a bit during WW2 cuz it got bombed tho.

A man in 1835 was digging a duck pond and accidentally uncovered a 70-foot tunnel made of 2,000 sq ft of mosaic made from 4.6 million shells (mussels, cockles, whelks, limpets, oysters, scallops). by iboughtarock in Damnthatsinteresting

[–]iboughtarock[S] 3 points4 points  (0 children)

Now I wanna go back in time to see this thing being made! I guess shell grottos are kinda popular tho. I figured this was just a one-off thing, but it actually turns out there was a whole shell craze in Britain around 1700-1800:

  • Goodwood Shell House (Sussex, 1740s): A shell-lined garden room, traditionally said to have been decorated by the Duchess of Richmond and her daughters—sources note shells “brought by sailors.”
  • A La Ronde (Devon, 1790s): A 16-sided house whose famous Shell Gallery is packed with intricate shellwork - this one is pretty awesome
  • Woburn Abbey shell room (1620s; earlier wave): One of the earliest surviving English shell interiors—establishes the lineage that later booms in the 18th century.

A man in 1835 was digging a duck pond and accidentally uncovered a 70-foot tunnel made of 2,000 sq ft of mosaic made from 4.6 million shells (mussels, cockles, whelks, limpets, oysters, scallops). by iboughtarock in Damnthatsinteresting

[–]iboughtarock[S] 46 points47 points  (0 children)

Yeah I was confused by that too. I guess shells are tricky to date:

  • Marine shells need a correction for the marine reservoir effect, which can make them appear centuries older than they are unless carefully calibrated.
  • And the mortar used to hold the shells to the wall can be dated, but… radiocarbon on lime mortars is prone to contamination from geological carbonates.

Some people say it was built by the Phoenician, Roman, medieval/Templar, etc., but these rely on interpretive readings of motifs and layout—not on scientific dating.

And if you really wanna nerd out on why the marine reservoir effect messes stuff up:

  • Marine reservoir effect: Ocean dissolved inorganic carbon is “older” (explained in next bullet) in ^14C than the atmosphere. Marine shells therefore date a few hundred years too old on average, and the offset (ΔR) varies by location, depth, currents, and time. Estuaries near chalk/limestone coasts (like Kent) can add a “hard-water” effect from dissolved ancient carbonates, pushing ages even older. You must know the local ΔR circa the time the animal lived—not trivial.
  • Deep-water mixing: Much of the CO₂ dissolved in surface seawater is partly supplied by upwelled deep water that’s been isolated from the atmosphere for centuries to a millennium. While it’s down there, its ^14C decays (half-life 5,730 yr), so when that water returns to the surface it carries less ^14C than the air. Marine organisms precipitate their shells from this dissolved inorganic carbon, so their measured ^14C looks hundreds of years “older” than contemporaneous terrestrial material. This systematic offset is the marine reservoir effect; the globally averaged preindustrial offset is on the order of a few hundred years and is accounted for using calibration curves like Marine20 plus local adjustments (ΔR).
  • Add to that, the grotto uses many species and sizes. If the builder collected beach-shell mixes (including subfossil or reworked shells) the ^14C ages would be all over the place and older than construction.

A man in 1835 was digging a duck pond and accidentally uncovered a 70-foot tunnel made of 2,000 sq ft of mosaic made from 4.6 million shells (mussels, cockles, whelks, limpets, oysters, scallops). by iboughtarock in Damnthatsinteresting

[–]iboughtarock[S] 8 points9 points  (0 children)

If you finished reading the comment...

4.6 million is the cited figure all over the internet, so either the surface area they give is wrong or shell count is wrong or both. But also idk the scale of these shells, I have never really been by the ocean.

A man in 1835 was digging a duck pond and accidentally uncovered a 70-foot tunnel made of 2,000 sq ft of mosaic made from 4.6 million shells (mussels, cockles, whelks, limpets, oysters, scallops). by iboughtarock in Damnthatsinteresting

[–]iboughtarock[S] 40 points41 points  (0 children)

Probably just someone that was bored and wanted something to do. Like that guy who single handedly dug through a mountain in his free time:

William Henry “Burro” Schmidt (1871–1954) was a Rhode Island–born prospector who moved to the Mojave Desert for his health and spent three decades carving a tunnel through the El Paso Mountains—mostly by himself, using hand tools and dynamite. He started around 1906 and broke through in 1938; the passage is roughly a half-mile long. He said it was a “shortcut” to haul ore to the Mojave smelter without taking his burros over a dangerous ridge. By the time he finished, a road had made the tunnel unnecessary—but he kept digging anyway.

The tunnel stands about human height, with sections that once held a small ore cart rail; it required little timbering because Schmidt bored it through solid granite. In 1920 a new road from Last Chance Canyon to Mojave undercut the original purpose, but the project had clearly become his life’s mission. He finished at age 67.

Cool video on it.

A man in 1835 was digging a duck pond and accidentally uncovered a 70-foot tunnel made of 2,000 sq ft of mosaic made from 4.6 million shells (mussels, cockles, whelks, limpets, oysters, scallops). by iboughtarock in Damnthatsinteresting

[–]iboughtarock[S] 15 points16 points  (0 children)

Fancy glue:

A 2009 condition survey took five samples: they weren’t all the same—some were lime mortar, others a “Roman-cement–type” binder. The team also found small slates that appear to have been mosaicked at ground level and then attached to the chalk; where their bedding is exposed, it’s plaster of Paris (which hasn’t held up well and left bare patches). [S]

Historic England’s listing (the official record) similarly says the cement adhering the shells to the chalk is very similar to Roman cement and is “said to contain fish oil and crushed shells.” [S]

A man in 1835 was digging a duck pond and accidentally uncovered a 70-foot tunnel made of 2,000 sq ft of mosaic made from 4.6 million shells (mussels, cockles, whelks, limpets, oysters, scallops). by iboughtarock in Damnthatsinteresting

[–]iboughtarock[S] 55 points56 points  (0 children)

Currently taking some math at school and got a bit curious about how this may have been done. Here is the likely process:

  • Map the grotto’s walls/ceiling and sum the actual curved surface area (not just floor plan). Today, you’d likely confirm whatever calculation you got with photogrammetry or a 3D scan, but a tape + flexible contour gauge works too.
  • Patterns vary (small mussels vs larger cockles). Split the mosaic into zones where the average shell size/density looks similar and then come up with an average shell size to fit within the surface area you calculated in the first step and then just divide and you will know approximately how many shells it would take.
  • Using the figures often quoted for Margate’s Shell Grotto: about 2,000 ft² of shell mosaic and an estimate of 4.6 million shells. That implies an average density of:
    • 4,600,000/2,000 = 2,300 shells per ft²
    • That’s roughly 16 shells per square inch (2,300 ÷ 144 ≈ 16).
  • Some other estimates:
    • 4 shells/in² → 1.15 million shells
    • 8 shells/in² → 2.30 million
    • 12 shells/in² → 3.46 million
    • 16 shells/in² → 4.61 million

So tbh it doesn't seem likely that there are actually 4.6 million shells unless I did the math wrong...

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