III. ANALYSIS AND SYNTHESIS. 15.) 



718. Five Wire Figures for representing Iiissajous' 

 Designs. Professor Buys-Ballot, Utrecht. 



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

 their shadows or lens images form the designs 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' 

 Figures. Professor 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 ; that 

 for showing the figure can be joined by a thread. 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 (two 

 rectangular) direction. 



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

 same pitch is designed 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, you have the 

 desired figure originated by both motions. 



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

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

 oscillation as you like. 



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

 octave of the other, } r ou take for the higher note a difference of phase double 

 as great as for the other, and so on. 



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

 jous' Figures. Professor W. F. Barrett. 



720. Melde's Universal Kaleidophon. 



Ferdinand 8uss, Marburg. 



(See Poggendorff's Annalen, vol. 114, p. 117.) 



This apparatus is too well known already to require in this place a 

 more detailed description as regards its capabilities. It will therefore be 

 necessary to give only a short explanation of the reading indications on the 

 Lamellae, and to refer, as to all specialities respecting this apparatus, to 

 Prof. Melde's publications. Poggendorffs Annalen, Vol. CXIV., page 117, 

 " Lehre von den Schwingungs-Curven," by Dr. Franz Melde, p. 25. 



The great Lamella has on each side a line as a mark, and on its upper end 

 the figures I. and II. ; the smaller Lamella have the same figures I. and II., 

 and on each side three lines. 



If the great Lamella is placed upon the mark of side I., and the small 

 Lamella on the line of side I., with the indication , then the vibrations of 

 both Lamellae to each other are as 1 : 4. The indications of side II. naturally 

 eorrespond to the mark of side II. on the great Lamella. 



The Lamella with the little mirror is used when the curves are to be shown 

 to a whole auditory, for which purpose the apparatus ought to be so placed 

 that the rays of the sun, or electric light, fall on the mirror, so that from 

 this the reflection is thrown either on the ceiling or on the wall of the room. 



