10 BULLETIN OP THE 



move his head, nor to open his ejes, but had to rely entirely 

 upon the sensations produced in his ears when his head was held 

 in a fixed position. 



The bearings of his hand were taken upon an imaginary sphere 

 in the centre of which he stood, and the reading was recorded 

 side by side with the true place of the telephone. 



After considerable experiment it was found advisable to use 

 only oue telephone, which was hung up in different parts of the 

 summer-house during the absence of the observer — as it was 

 found that the observer soon came to recognize each individual 

 telephone by the quality or timbre of the sound produced by it 

 — and that this recognition biassed his judgment regarding the 

 direction of the soimd., 



'Imagine the observer to be facing the north — then the direction 

 of sounds produced at the easterly or westerly points of the hori- 

 zon of the ears was always clearly perceived. In proportion as 

 the angular distance of the source of sound from those points 

 was increased the readings of the observers became wild, and 

 when it was 90° it was not uncommon to make a mistake of 180° 

 in the direction of the sound. 



The general results of all the observations thus seem to agree 

 very closely with those obtained by telephone ; but an examina- 

 tion of the individual records must convince one that an indi- 

 vidual observer discriminates the direction of a sound to a 

 much greater extent than that indicated by the experiments first 

 narrated. Most observers could indicate correctly the direction 

 of sounds that proceeded from the northerly or southerly points 

 of the horizon of the ears ; few could locate a sound from the 

 zenith, and none could tell the direction of a sound from beneath. 



When a telephone was placed on the ground between the feet 

 of the observer, and was there caused to sound — he would imme- 

 diately form a mental conception of the direction of the sound, 

 and would indicate it by pointing, but he was invariably mistaken. 



Mr. Bell stated that he thought that the method pursued would 

 ultimately lead to valuable results, but that many more experi- 

 ments were necessary ; and the results so far obtained he pre- 

 sented to the Society in a tabulated form. 



