184 SEC. 6. SOUND. 



718. Five Wire Figures for representing Lissajous' 

 Figures. Prof. Buys-Ballot, Utrecht. 



On a horizontal wooden rod are placed five figures of wire, so bent that 

 their shadows or lens images form the figures of Lissajous. Each interval 

 has its own wire figure, and the changes produced by various phase- 

 differences are shown by turning the figures round their vertical axes. 



719. Wooden Board for constructing Lissajous 9 

 Figures. Prof. Buys-Ballot, Utrecht* 



The instrument consists of a white-painted wooden board, on which a 

 circle is traced. Horizontal and vertical lines cut the circle in points 

 corresponding to the angles of a regular inscribed icosagon. At the inter- 

 section of each pair of lines a hole is made in the board for fixing pins, which 

 can be joined by threads for showing the figure. Along one of the hori- 

 zontal and vertical sides of the board two rods can be fixed, provided with 

 ciphers corresponding with the horizontal and vertical lines. Each of 

 these lines may be figured to represent the phase of a vibrating particle either 

 by sound or light for each twentieth part of a vertical and horizontal 

 direction. 



For instance, the figure exhibited by the interference of two notes of the 

 same pitch is constructed in the following manner: The horizontal rod 

 indicates the vertical chords on which the particle is at a supposed moment 

 by a horizontal vibration, then the perpendicular rod indicates in the same 

 manner the horizontal on which it would be at the same moment by a 

 vertical vibration. By fixing pins at the intersections of those chords 

 indicated by the same ciphers, and joining them by a thread, the desired 

 figure originated by both motions is obtained. 



If the oscillations differ in phase, another rod not beginning with the same 

 cipher, but with another differing as many twentieth parts of the oscillation 

 as required is found. 



If the two interfering notes are not of the same pitch, but one figure is the 

 octave of the other, for the higher note a difference of phase double as great 

 as for the other is taken, and so on. 



719a. Tonophant, a simple arrangement for showing Lissa- 

 jous' Figures. Sec Phil. Mag., Sept. 1868. 



Prof. W. F. 'Barrett. 



719b. Apparatus for exhibiting the combination of 



rectangular Vibrations, made by Yeates & Son, Dublin. 



Prof. W. F. Barrett. 



By turning the handle the two mirrors have a vibratory motion imparted 

 to them in planes at right angles to each other ; the relative rate of vibration 

 of the mirrors can be adjusted by a simple mechanical contrivance. A beam 

 of light reflected from one mirror to the other and projected on a screen thus 

 enables a large audience to see the whole of Lissajous' figures. 



1576a. Wheatstone Kaleidophone. 



The British Telegraph Manufactory, Limited. 



1576b. Wheatstone Kaleidophone. 



The British Telegraph Manufactory, Limited. 



720. Melde's Universal Kaleidophon. 



Ferdinand Suss, Marburg* 

 (See Poggendorffs Annalen, vol. 114, p. 117.) 



