The More You Nerd: Deckle Edge

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Definition via Merriam-Webster Online Dictionary
Deckle edge, date: circa 1874: 
the rough untrimmed edge of paper left by a deckle or produced artificially.
Or check out the definition of Deckle.

The deckle is he frame in which paper is made. The pulp oozes toward the edges of the frame and some seeps through creating a rough, uncut edge.

A while on later they created a continuous style paper making frame, but the top and bottle would still have the rough edges.

Today, the deckle edged paper is cut by machines to purposefully copycat this early method of paper making.
Some people hate it (Good lord, who!?), but if you’re like me you love it. One of my favorite things about the Lemony Snicket books were the edges of the paper-yes, it was nice in other ways.
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Why should I care?
You know just a little bit more about the world and history.

Why did I research it? During cave tours, I compare the layered limestone rocks in the cave to the the deckle edge of books, but no matter how the edges are trimmed the pages will be flat when you open the book. People always ask why the ceiling is so flat. It is sedimentary rock, and I figured this was a decent answer.

Further Nerding:
I remember making paper when I was a kid for summer reading program. I was maybe 8 or 9 and I remember it being quite fun.

I read this article on The Economist and found it to be quite interesting. There is even a bit of snarkiness at the end.