THE SENSE OF HEARING 



229 



at three points of its periphery A, B, C. The opening A serves, as in 

 Helmholtz' resonators, to receive the sound-waves ; the lumen of this 

 aperture, unlike Helmholtz' resonators, can be altered at will by means of 

 diaphragms (d, e) which can be screwed to the end of the tube A, F. On 

 varying the lumen of this diaphragm, the proper tone of the resonator alters, 

 and Kdelmanii provides diaphragms of different apertures, by which the 

 proper tone of the resonator can be varied exactly from semitone to semitone. 



FIG. 91. Series of.'resonators ; Edelmann's new model. 



The semitones which can be analysed by these resonators are 72, and form 

 the 6 octaves from of the contra-octave to c of the 4 times accented octave 

 (from 32-33 to 2068 -6 d.v.). 



The opening C serves for hearing, while the opening B, which is absent in 



f 



F 



5 1 " 



Fir;. 02. Section through one of Edelmann's resonators. 



Helmholtz' resonators, is made air-tight by a thin, circular plate of resonat- 

 ing wood, and conducts the sound-waves from an instrument placed directly 

 against it to the air contained inside the resonator. This is particularly 

 advantageous in the analysis of feeble tones, which cannot be analysed 

 with Helmholtz' resonators because their waves are weakened by transmis- 

 sion through the air. 



Even without the aid of hearing, the compound nature of 

 tones can be demonstrated physically by the Konig's flame 

 manometer (Vol. III. p. 131). 



