ears to rotate in the same
direction as the revolution; Fig. 2 appears to revolve in the
opposite direction, and Fig. 3 appears to revolve sometimes in the
same direction and at other times in the opposite direction.

A curious effect can be produced with Fig. 1 by covering up Figs.
2 and 3 with a piece of plain paper and laying a coin or other
small object on the paper. If the vision is then concentrated on
the coin or other object while same is being revolved, Fig. 1 will
be seen to rotate.

** Barrel-Stave Hammock [75]

A hammock made of barrel staves is more comfortable than one would
think, considering the nature of the material employed in making
it. Good smooth staves should be selected for this purpose, and if
one cares to go to little trouble a thorough sandpapering will
make a great improvement. Cut half circles out of each stave, as
shown at AA, and pass ropes around

[Illustration: Cheap and Comfortable]

the ends as shown at B. When finished the weight will then be
supported by four ropes at each end, which allows the use of small
sized ropes, such as clothes lines. A hammock of this kind may be
left out in the rain without injury.
--Contributed by H.G.M., St. Louis, Mo.

** A Singing Telephone [75]

Those who have not already tried the experiment may be interested
to know that a telephone may be made to sing by holding the
receiver about 1/16 in. from the transmitter, as shown in the
illustration. The experiment will

[Illustration: To Make a Telephone Sing]

work well on most telephones, but not on all.

When the receiver is placed in the position shown it acts like an
ordinary buzzer, and the function of the transmitter will then be
that of an interrupter. The slightest movement of the transmitter
diaphragm will cause an increased movement of the receiver
diaphragm. This in turn will act on the transmitter, thus setting
up sympathetic vibrations between the two, which accounts for the
sound.

** A Microscope Without a Lens [76]
By E. W. DAVIS

Nearly everyone has heard of the pin-hole camera, but the fact
that the same principle can be used to make a microscope, having a
magnifying power of 8 diameters (64 times) will perhaps be new to
some readers. To make this lensless microscope, procure a wooden
spool, A (a short spool, say 1/2 or 3/4 in. long, produces a
higher magnifying power), and enlarge the bore a little at one
end. Then blacken the inside with india ink and allo