first place them
on the diagram, as shown in the illustration, and the puzzle is to get
them into regular alphabetical order, as follows:--

A B C D
E F G H
I J K L

The moves are made by exchanges of opposite colours standing on the same
line. Thus, G and J may exchange places, or F and A, but you cannot
exchange G and C, or F and D, because in one case they are both white
and in the other case both black. Can you bring about the required
arrangement in seventeen exchanges?

[Illustration]

It cannot be done in fewer moves. The puzzle is really much easier than
it looks, if properly attacked.

235.--TORPEDO PRACTICE.

[Illustration]

If a fleet of sixteen men-of-war were lying at anchor and surrounded by
the enemy, how many ships might be sunk if every torpedo, projected in a
straight line, passed under three vessels and sank the fourth? In the
diagram we have arranged the fleet in square formation, where it will be
seen that as many as seven ships may be sunk (those in the top row and
first column) by firing the torpedoes indicated by arrows. Anchoring the
fleet as we like, to what extent can we increase this number? Remember
that each successive ship is sunk before another torpedo is launched,
and that every torpedo proceeds in a different direction; otherwise, by
placing the ships in a straight line, we might sink as many as thirteen!
It is an interesting little study in naval warfare, and eminently
practical--provided the enemy will allow you to arrange his fleet for
your convenience and promise to lie still and do nothing!

236.--THE HAT PUZZLE.

Ten hats were hung on pegs as shown in the illustration--five silk hats
and five felt "bowlers," alternately silk and felt. The two pegs at the
end of the row were empty.

[Illustration]

The puzzle is to remove two contiguous hats to the vacant pegs, then two
other adjoining hats to the pegs now unoccupied, and so on until five
pairs have been moved and the hats again hang in an unbroken row, but
with all the silk ones together and all the felt hats together.

Remember, the two hats removed must always be contiguous ones, and you
must take one in each hand and place them on their new pegs without
reversing their relative position. You are not allowed to cross your
hands, nor to hang up one at a time.

Can you solve this old puzzle, which I give as introductory to the next?
Try it with counters of two colours or with c