228 Lord Kayleigli on our 



of silence representing phase-opposition varies with the 

 position in the room of the ear of the assistant observer. 

 To secure a satisfactory signal at the higher pitches, this 

 position requires to be carefully chosen. In the later expe- 

 riments a resonator was always employed, whose mouth was 

 symmetrically situated with respect to the open ends of the 

 pipes, which are the proximate sources of sound, connexion 

 with the ear of the assistant observer being through a suitable 

 rubber tube. After this there was no ambiguity, the rule of 

 the lower pitch being uniformly followed. But when the open 

 ends of the pipes were not very close to the ears, perhaps 

 2 inches distant, the right and left effects seemed to two 

 observers (including myself) not only to be rather obscured, 

 but to be concentrated into the neighbourhood of phase- 

 opposition. A third observer, however, heard the right and 

 left effects more strongly, and with less apparent concentration 

 towards phase-opposition. 



On the theory that passage of sound round the head had 

 something to do with these complications, the open ends of 

 the pipes were brought much closer to the ears, but without 

 fitting air-tight, the resonators being re-adjusted so as to 

 diminish the loudness. In this condition of things the two 

 observers experienced the right and left effect more normally 

 and without special concentration in the region of phase- 

 opposition. But the observation is certainly more difficult 

 than at lower pitches, and I believe that the effects are really 

 less pronounced. 



Experiments similarly conducted with forks of pitch c" (512) 

 gave results of the same character. When the open ends of 

 the pipes were quite close to the ears, the right and left effect 

 was pretty good and fairly distributed. In this three ob- 

 servers concurred. But a slight withdrawal of the pipes 

 introduced confusion, the extent of which, however, appeared 

 to vary with the observer. In all cases the right and left 

 effects, when sufficiently marked to be observed, obeyed the 

 sequence rule. 



At pitch e" (640) the results were not very different. The 

 open ends of the pipes being close to the ears, but not fitted 

 air-tight, only pretty good right and left effects could be 

 observed, and these appeared to be crow r ded towards phase- 

 opposition. The sequence rule was obeyed. 



Finally, trials by the same method were made with forks 

 of pitch g" (6x128 = 768). No particular difficulty was 

 encountered in satisfying the necessary experimental con- 

 ditions, but the results were of a nondescript character. 

 Even when the open ends of the pipes were close to the ears, 



