- Ones, Numbers composed only of, 18, 75, 198.
- Opposition in Chess, 224.
- Orchards, The Fifteen, 143, 241.
- Ovid's Game, 156, 248.
- Oxen, The Farmer's, 157, 248.
- Ozanam's Recreations, 246.
- Packing Puzzles, Measuring, Weighing, and. See Measuring.
- Palindromes, 17.
- Pardoner's Puzzle, The, 25, 164.
- Parental Command, A, 28.
- Park, Mystery of Ravensdene, 105, 211.
- Parson's Puzzle, The, 47, 177.
- Party, The Squire's Christmas Puzzle, 86, 205.
- Pellian Equation, 197.
- Pennies, The Eleven, 88, 206.
- Phials, The Two, 42.
- Photograph, The Ambiguous, 94, 210.
- Pie and the Pasty, The, 36.
- Pilgrimages, The Fifteen, 25.
- Pilgrims' Manner of Riding, 34.
- Pilgrims The Riddle of the, 70, 194.
- Pillar, The Carved Wooden, 31.
- Plato and the Nines, 154, 247.