[Illustration]
Take a common tuning-fork, and on one of its branches fasten with
sealing-wax a circular piece of card, of the size of a small wafer, or
sufficient nearly to cover the aperture of a pipe, as the sliding of
the upper end of a flute with the mouth stopped: it may be tuned in
unison with the loaded tuning-fork (a C fork), by means of the moveable
stopper or card, or the fork may be loaded till the unison is perfect.
Then set the fork in vibration by a blow on the unloaded branch, and
hold the card closely over the mouth of the pipe, as in the engraving,
when a note of surprising clearness and strength will be heard. Indeed,
a flute may be made to “speak” perfectly well, by holding close to the
opening a vibrating tuning-fork, while the fingering proper to the note
of the fork is at the same time performed.