Write the alphabet into a five by five square. Because 26 letters will not fit in 25 cells, I and J share a cell â the rest of the word tells you which one is meant. Each letter becomes its row number followed by its column number, so WATERMELON starts 52 11 44.
Talking to the next hill with torches
Polybius, a Greek historian, wanted to send words across a valley. His answer: hold up torches in two groups. The first group counts out the row, the second counts out the column, and together they name a letter. Armies had been signalling “attack” or “retreat” with fires for centuries; Polybius worked out how to spell.
Print this page and you get a worksheet: how the cipher works, where it came from, and the puzzles to crack, with the machine and the menus left off.
Print this page as a worksheet Its sheet in the pack Try the challengesLonger, harder and written for grown-ups. Worth a look when this page runs out.