July 20, 1882] 



NATURE 



277 



intensity occur in those wave-forms which yield a sudden 

 and brief maximum condensation. It is clear, also, that 

 as the phase o and the phase \ are not identical, the action 

 on the ear is not the same when a sudden condensation 

 is produced and dies away gradually, as when a con- 



densation gradually rises to its maximum and then sud- 

 denly falls off. It may be added, that no explanation of 

 this very novel result has yet been advanced from a 

 theoretical point of view. 



There only remains one small detail of interest to 



Fig. 5,— Kcenig's Wa 



narrate. Observing that wave-forms in which the waves 

 are obliquely asymmetrical — steeper on one side than on 

 the other — are produced as the resultant of a whole series 

 of compounded partial tones, it occurred to Kcenig to 

 produce from a perfect and symmetrical sinusoidal wave- 



vertical slit, such as a b, a perfectly simple tone, devoid 

 of upper partials, is heard. But by inclining the slit, as 

 at ab\ the same effect is produced as if the wave-form 

 had been changed to the oblique outline d g' I' n' p' r V v', 

 the slit remaining upright all the while. But this oblique 



O 



o 



Fig. 6.— Positions of the slits in front of the wave-disks for combining the 

 sounds with phase-difference |. 



curve a complex sound, by the very simple device of 

 turning the slit, through which the wind was blown 

 against it, into an oblique position. 



In Fig. 10 is drawn a simple symmetrical wave-form 

 eglnprtv. If a series of these are passed in front of a 



Fig. -7. — Position of the slits fur phase-difference \. 



form is precisely like that obtained as the resultant of a 

 decreasing series of partial tones (see Fig. 4, a). If the 

 slit is inclined in the same direction as the forward move- 

 ment of rotation of the wave-disk, the quality produced is 

 the same as if all the partial tones coincided at their 



