The cross word puzzle book: Second series (1924)
“ You will notice also that all the words in the puzzle are joined together or interlocked so that after guessing the first word the solver may decode the entire puzzle without once being minus a hint of some sort. I do not mean to infer that these puzzles must be so constructed that the solver has a simple task. An object of crosswording is to puzzle, but fairness to a hard working puzzler dictates certain laws for the designer to follow. The first of these laws is the all-over interlock. The second is that in obsolete, rare, and unfamiliar words no letter should be unkeyed. ”
