Ball, W. W. Rouse (Walter William Rouse), 1850-1925 · London, Macmillan · leaf 246
CH. x1] MISCELLANEOUS PROBLEMS 225 cell or small square empty; the puzzle is to move them so that finally they occupy the position shown in the first of the annexed figures, D Top of Box C … A Bottom of Box B We may represent the various stages in the game by sup- posing that the blank space, occupying the sixteenth cell, is moved over the board, ending finally where it started. The route pursued by the blank space may consist partly of tracks followed and again retraced, which have no…
