I wish I had been smart enough or educated enough to have written this article, but I won't take credit for having known all of this stuff. I will direct you, instead, to the original article from the Mental Floss blog.
Letters that didn't make the cut (I cannot write them correctly, cause I don't know how to find them in the available scripts on my computer, but) are:
1. Thorn (looks a lot like a small letter p);
2. wynn (also looks like a small letter p, but shaped differently);
3. yogh (looks like the number 3, and makes the gutteral ch sound like in "Bach");
4. ash (ae joined);
5. eth (like a letter d that you cross like a t);
6. & (was a letter that came at the end of the alphabet and meant "and per se and");
7. insular g (resembled a g at the bottom, but was open at the top - difficult to describe; morphed through several pronunciations);
8. tht (seen in churches; like a p with a tall stem above the circle, that is crossed like a t);
9. ethel (oe blend);
10. Triond "ond" (like a 7, but with a straight stick, or a crossed stick);
11. Long s (looks like f, like when you see in an old book "Paradife Loft")
12. eng (an altered letter n)
I love articles like this that stretch my brain. I am a life-long learner, and this article was so much so fast that I can't wrap my brain around all of it so quickly. So I will have to go back and review the material several times so I can absorb it better.
There was also a link at the bottom of the article that I plan to check out, "You also might be interested in", about why I sneeze in the sunshine. I will want to read that, because I've noticed that since I was a little kid.
Hope you enjoyed this link to Mental Floss.