Magic tricks -- Juvenile literature; Scientific recreations -- Juvenile literature
On vibrating bodies, which present a large surface, the effects of
sounds are very surprising. Persons with a clear and powerful voice
have been known to break a drinking-glass, by singing the proper
fundamental note of their voice close to it. Looking-glasses are also
said to have been broken by music, the vibrations of the atoms of the
glass being so great as to strain them beyond the limits of their
cohesion.
FIGURES PRODUCED BY SOUND.
Stretch a sheet of wet paper over the mouth of a glass tumbler, which
has a footstalk, and glue or paste the paper at the edges. When the
paper is dry, strew dry sand thinly upon its surface. Place the tumbler
on a table, and hold immediately above it, and parallel to the paper,
a plate of glass, which you also strew with sand, having previously
rubbed the edges smooth with emery powder. Draw a violin bow along any
part of the edges, and as the sand upon the glass is made to vibrate,
it will form various figures, which will be accurately imitated by the
sand upon the paper; or, if a violin or flute be played within a few
inches of the paper, they will cause the sand upon its surface to form
regular lines and figures.
TRANSMITTED VIBRATION.
[Illustration]
Provide a long, flat glass ruler or rod, as in the engraving, and
cement it with mastic to the edge of a drinking-glass fixed into a
wooden stand; support the other end of the rod very lightly on a
piece of cork, and strew its upper surface with sand; set the glass
in vibration by a bow, at a point opposite where the rod meets it,
and the motions will be communicated to the rod without any change in
their direction. If the apparatus be inverted, and sand be strewed on
the under side of the rod, the figures will be seen to correspond with
those produced on the upper surface.
DOUBLE VIBRATION.
[Illustration]
Provide two discs of metal or glass, precisely of the same dimensions,
and a glass or metal rod; cement the two discs at their centres to
the two ends of the rod, as in the engraving, and strew their upper
surfaces with sand. Cause one of the discs, viz. the upper one, to
vibrate by a bow, and its vibration will be exactly imitated by the
lower disc, and the sand strewed over both will arrange itself in
precisely the same forms on both discs. But if, separately, they do not
agree in their tones, the figures on them will not correspond.
CHAMPAGNE AND SOUND.
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