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PREFACE

When preparing this new edition for the press, my first inclination was
to withdraw a few puzzles that appeared to be of inferior interest, and
to substitute others for them. But, on second thoughts, I decided to let
the book stand in its original form and add extended solutions and some
short notes to certain problems that have in the past involved me in
correspondence with interested readers who desired additional
information.

I have also provided--what was clearly needed for reference--an index.
The very nature and form of the book prevented any separation of the
puzzles into classes, but a certain amount of classification will be
found in the index. Thus, for example, if the reader has a predilection
for problems with Moving Counters, or for Magic Squares, or for
Combination and Group Puzzles, he will find that in the index these are
brought together for his convenience.

Though the problems are quite different, with the exception of just one
or two little variations or extensions, from those in my book _Amusements
in Mathematics_, each work being complete in itself, I have thought it
would help the reader who happens to have both books before him if I made
occasional references that would direct him to solutions and analyses in
the later book calculated to elucidate matter in these pages. This course
has also obviated the necessity of my repeating myself. For the sake of
brevity, _Amusements in Mathematics_ is throughout referred to as _A. in
M._

HENRY E. DUDENEY.

THE AUTHORS' CLUB,
_July 2, 1919._

INTRODUCTION

Readers of _The Mill on the Floss_ will remember that whenever Mr.
Tulliver found himself confronted by any little difficulty he was
accustomed to make the trite remark, "It's a puzzling world." There can
be no denying the fact that we are surrounded on every hand by posers,
some of which the intellect of man has mastered, and many of which may be
said to be impossible of solution. Solomon himself, who may be supposed
to have been as sharp as most men at solving a puzzle, had to admit
"there be three things which are too wonderful for me; yea, four which I
know not: the way of an eagle in the air; the way of a serpent upon a
rock; the way of a ship in the midst of the sea; and the way of a man
with a maid."

Probing into the secrets of Nature is a passion with all men; only we
select different lines of research. Men have spent long live