1. Introductory (p. 185). 2. The inverse proportion between 'sharpness of tuning' aid. 'persistence' of resonators of different pitch, armrdiug to physical coizsiderations (p. 186). 3. The inverse proportion between the 'sharpness of tuiziq' and 'persistence ' i n the ear, according to auditory experiinent (pp. 187-190). 4. Obedience to Weber's law (pp. 190-193). (pp. 193, 194). 6. Sunzinury (p. 194). . Principal experimental evidence i n favour of the resonance theory 1. IN discussing the

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... ionship between the persistence and the sharpness of tuning of resonators, Helmholtz describes tests which show that shakes and trills which appear quite sharp and musical when executed a t a certain rate in the treble, appear bad and rough when performed a t the same rate in the bass. He points out that these.facts prove that "there must be different parts of the ear that are set in vibration by tones of different pitch and which receive the sensation of these tones," or in other words that the ear contains a series of resonators. I find on the lines of this suggestion that it is possible to test by experiment whether there are resonators in the ear or not. The test is based on the following facts: (a) That the tuning coefficients and persistence coefficients of resonators of different pitch are inversely proportional to one another. ( b ) That the tuning and persistence coefficients of the ear for the perception of notes of different pitch are inversely proportional, and therefore the ear must contain resonators.