Place these over the eyepiece of the
telescope and secure in place with rubber bands looped over the
nibs and around the barrel of the instrument.
--Contributed by R. A. Paine, Richmond, Va.
** How to Make an Electrical Horn [218]
Secure an empty syrup or fruit can, any kind having a smooth flat
bottom will do. If the bottom is not perfectly flat, it will
interfere with the regular tone vibrations, and not produce the
right sound. Remove the label by soaking it in hot water. Take an
ordinary electrical bell and remove the gong, clip off the
striking ball and bend the rod at right angles. Cut a block of
wood 3/4 in. thick, 5 in. wide and 8 in. long for the base. Fasten
the can on it with a piece of sheet brass or
[Illustration: Tin Can and Bell Parts]
tin as shown in the sketch. Mount the bell vibrator on the base,
using a small block of wood to elevate it to the level of the
center of the can, and solder the end of the vibrator rod to the
metal.
Connect two dry cells to the bell vibrator, and adjust the contact
screw until a clear tone is obtained. The rapidly moving armature
of the bell vibrator causes the bottom of the can to vibrate with
it, thus producing sound waves.
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