An index is a piece of technology, and it had to be invented. Ancient scrolls co not ca one, bec a scr has n stable pa to po at, a a rea looking f a passage simply had to unroll the thing and search. The bound book changed that, and within two centuries scholars were compiling alphabetical lists that let a reader enter a long text at any point they chose.

Type only the missing letters. Each box is one letter, and the number of boxes matches the letters that are missing.