Arithmetical recreations. — Geometrical recreations. — Mechanical recreations. — Chessboard recreations. — Magic squares. — Unicursal problems. — Kirkman's school-girls problem. — Miscellaneous problems. — The mathematical tripos. — Three classical geometrical problems. — The parallel postulate. — Insolubility of the algebraic quintic. — Mersenne's numbers. — String figures. — Astrology. — Cryptographs and ciphers. — Hyper-space. — Time and its measurement. — Matter and ether theories