LIST OF FIGURES.

1. Seebeck's Siren, 11c
2, 3, 4. Cagniard de la Tour's Siren, 12b
5. Tuning-fork tracing its Curve, 20b
6. Curve traced in Phonautograph, 20d
7. Curve of Simple Vibration, 21b
8. Curve of Motion of Hammer moved by Water-wheel, 21c
9. Curve of Motion of Ball struck up on its descent, 21c
10. Reproduction of fig. 7, 23d.
11. Curve showing the Composition of a simple note and its Octave in two different phases, 30b, c
12. Curve showing the Composition of a simple note and its Twelfth in two different phases, 32b
13. Tuning-fork on Resonance Box, 40a
14. Forms of Vibration of a Circular Membrane, 40c, d
15. Pendulum excited by a membrane covering a bottle, 42a
16. a. Spherical Resonator, 43b
b. Cylindrical Resonator, 43c
17. Forms of Vibration of Strings, 46a, b
18. Forms of Vibration of a String deflected by a Point, 54a, b
19. Action of such a String on a Sounding-board, 54c
20. Bottle and Blow-tube for producing a simple Tone, 60c
21. Sand figures on circular elastic plates, 71c
22. The Vibration Microscope, 81b
23. Vibrations as seen in the Vibration Microscope, 82b
24. Vibrational Forms for the middle of a violin string, 83b
25. Crumples on the vibrational form of a violin string, 84b
26. Gradual development of Octave on a violin string bowed near the bridge, 85b
27. An open wooden and stopped metal organ flue-pipe, 88
28. Free reed or Harmonium vibrator, 95b
29. Free and striking reed on an organ pipe partly in section, 96a, b
30. Membranous double reed, 97a
31. Reproduction of fig. 12, 120a, b
32. Fork with electro-magnetic exciter, and sliding resonance box with a lid (artificial vowels), 121b

33. Fork with electro-magnet to serve as interrupter of the current (artificial vowels), 122b
34. Appearance of figures seen through the vibration microscope by two forks when the phase changes but the tuning is correct, 126d
35. The same when the tuning is slightly altered, 127a
36. Construction of the ear, general view, with the auditory canal original: "meātus audītōrius", labyrinth, cochlea, and Eustachian tube, 129c
37. The three auditory ossicles—hammer, anvil, and stirrup—in their relative positions, 130c
38. Two views of the hammer of the ear, 131b
39. Left temporal bone of a newly-born child with the auditory ossicles in place original: "in situ", 131c
40. Right drumskin with hammer seen from the inside, 131c
41. Two views of the right anvil, 133a
42. Three views of the right stirrup, 134a
43. A, left labyrinth from above, 136b, c. B, right labyrinth from within. C, left labyrinth from without.
44. Utriculus and membranous semicircular canals (left side) seen from without, 137a
45. Bony cochlea (right side) opened in front, 137c, d
46. Transverse section of a spire of a cochlea which has been softened in hydrochloric acid, 138a, b
47. Max Schultze's hairs on the internal surface of the epithelium in the ampullae, 138c, d
48. Expansion of the cochlear nerve, 139c
49. Corti's membrane, 140a, b, c
50. Corti's rods or arches separate, 140d
51. Corti's rods or arches in place original: "in situ", 141b, c
52. Diagram of the law of decrease of sympathetic resonance, 144c, d
53. Interference of similarly disposed waves, 160b
54. Interference of dissimilarly disposed waves, 160c
55. Lines of silence of a tuning-fork, 161c
56. The Polyphonic Siren, 162
57. Diagram of origin of beats, 165a