362 



Messrs. W. H. Preece and A. Stroh. [Feb. 27, 



a small counterbalancing weight ("W), and at its longer end a glass 

 pen (Q) containing suitable ink. On the table It is placed a piece of 

 paper or smoked glass, which is held thereby two spring clamps. Each 

 of the eight wheels has on its face a number of small holes or pits, into 

 which the points of the rods B' can be placed, and these are arranged 

 in eight rows radiating from the centre. When one of the rods, for 

 instance that belonging to the wheel B, is placed in position B", as 

 indicated by the dotted lines, and motion is given to the wheels by 

 means of the crank on the axle belonging to the wheel I, the crank- 

 like movement of the rod B' will, by means of the silk thread 

 roller N', levers TJ, V, and O, cause the pen Q to move to and fro 

 with simple harmonic motion, while the table hi will move longi- 

 tudinally, the pen thereby writing on the joaper a simple harmonic 

 curve. This can be done with each of the eight rods separately, the 

 result being in each case a simple curve. Should, however, two or 

 more rods be placed on the faces of the wheels, the result will be a 

 curve compounded of the sum of the several simple curves. In order 

 to increase or decrease the amplitude of a curve, the steel rods are 

 placed further from, or nearer to, the centre of the wheels. Difference 

 of phase is obtained by shifting the rods to the different radial rows of 

 holes on the face of the wheels. Three additional wheels, K, L, M, 

 have been fitted, making 10, 12 and 16 revolutions respectively, to one 

 turn of the wheel A, and the rods belonging to neighbouring wheels 

 are so arranged that they can be borrowed for the use of these smaller 

 wheels if desirable. 



12. Besides assuming the pitch to be constant, it has also been 

 assumed that each octave of the partial, to maintain equal loudness of 

 sound, must diminish one half in amplitude as it rises. Thus the 



First Octave is J the amplitude of the prime. 

 Second „ J „ „ 



Third „ J 

 Fourth „ T V 

 The intermediate notes, such as the third and the fifth, decrease in 

 intermediate ratio. 



13. This instrument enables us to form synthetically all the curves 

 produced by vowel tones, and to show how these tones are com- 

 pounded of primes and harmonic upper partials. It shows how simple 

 tones can be produced by simple harmonic curves, and compound tones 

 by the simultaneous action of several simple tones. 



The following figure (fig. 5), shows the simple harmonic curve 

 produced by each wheel, and several examples of curves formed by 

 different components. In this way curves have been reproduced as 

 shown in fig. 6, representing the vowel sounds based on Helmholtz's 

 theory, as indicated by Mr. Ellis in a tabular statement, at page 181 

 -of his translation of Helmholtz's work. 



