Tuning forks are built to vibrate at a specific frequency in the acoustic range. Some of the forks in this set have brass sliders on their prongs that can be set to marked positions to adjust the frequency. See image P0919B.

This set of 8 forks is built to demonstrate Lissajous figures, which are the patterns produced when vibrations at two different frequencies are displayed at right angles. For this purpose a mirror is mounted on the tip of one of the prongs, with a spherical compensating mass on the other prong. A narrow beam of light can be reflected off the mirror on one fork and then off the mirror on another one positioned so as to deflect the beam in a perpendicular direction. The beam produces a spot of light on a screen and this executes the Lissajous figure for the frequencies chosen. We only have the set of forks, not the apparatus to maintain the vibration electrically or demonstrate the figures.

The marked frequencies and other details of the set are as follows:
UT1 128 vs (i.e.Hz) with attachments
UT1 RE1 128 - 148 vs
MI1 FA1 148 - 174 vs
SOL1 - - 174 - 210 vs
UT2 256 vs
LA1 SI1 UT2 210 - 256 vs
MI2 320 vs
SOL2 384 vs (mirror and sphere missing)

Set matches original record of purchase from Bouron in April 1908

Inscriptions / Translations:  RK Monogram

Notes:  Purchased from Bouron in 1908