_The Reels and String Puzzle_ is highly entertaining. The only materials
required for it are the lid of a cigar box, two cotton reels, two
beads, and a length of smooth string or thin silk cord. The making is
simplicity itself. All you need do is cut the lid in halves and bore
three holes in a line in one of the halves. Of course you can ornament
your wood as much as you like, but that will in no way increase or
decrease the effectiveness of the puzzle.
When you have cut it out and finished it off nicely with glass-paper,
thread the beads and reels as shown in Fig. 57. Take special care that
you do not make any mistake in the arrangement, or your solution will
result in a hopeless tangle.
[Illustration: FIG. 57.]
The object of the puzzle is to get the two cotton reels, which, as you
see, are now on quite separate loops, on to one loop. To solve it
proceed as follows: Take hold of the centre loop, and pull it down to
its full extent. Now pass the right-hand reel through the loop. Taking
care not to twist the cord, pass this loop through the hole on the
right-hand side, over the bead, and then draw it back again.
Now if you follow the same procedure with the left-hand reel you will
find that the centre loop is released and can be pulled through the
centre hole. Then will the two reels slide down side by side.
One thoroughly entertaining and, to a certain extent, bewildering puzzle
is
_The Three-hole Puzzle._--Really the puzzle consists of a piece of thin
wood with three holes cut in it. These three holes are respectively
circular, square, and triangular (Fig. 58). The problem is to cut one
block of wood which will pass through each hole and at the same time fit
the hole exactly.
[Illustration: FIG. 58.]
Can it be done? At first it looks to be quite impossible; but there is a
very neat solution to the difficulty.
First cut out your holes. To do this get a cigar-box lid and draw out
the three figures, taking care that the length of the side of the square
and the length of the side of the triangle and the length of the
diameter of the circle are equal. Now, using your fret saw, cut out
these holes very neatly and precisely.
For the block you need a small cylinder of wood: an odd piece of broken
broom handle will do admirably. This must be cut and finished with
glass-paper so that it will fit the circular hole exactly. Now saw a
piece just as long as the cylinder is wide. This looked at in one way
gives an exact square which will fit the second hole. Thus two holes are
catered for.
Finally, for the third hole the cylinder must be tapered on two sides.
To do this draw a diameter at one end and then gradually pare away a
flat surface till the triangular section is obtained.
Fig. 59 shows how the block, when turned in different ways, fits the
three holes.
[Illustration: FIG. 59.]