FIG. LIST OF ILLUSTRATIONS. 1.-Vibrations of Stretched String. 2.-Harmonic Sounds. Nodes and Ventral Segments of Vibrating String . 3.-Harmonics. Nodes and Ventral Segments of a V brating String 11.-A Tuning-fork mounted on a Sounding-box. 12.-Vibrations of a Plate. 13.-Nodal Lines of Vibrating Circular, or Polygonal Plate according to Chladni and Savart. 14.-Nodes and Segments of a Vibrating Bell 15. Section of a Bell 16.-Proof of the Vibration of a Glass Bell 0.-Beats of Imperfect Unison. time. 2. Sums of the Corresponding Ordinates 3.-Savart's Toothed Wheel 4 -Philosophical Lamp or Chemical Harmonicon. 6.—Experimental Study of the Laws of Reflection of Sound 9.-M. Helmholtz's Resonance Globe 1.-Ordinates of Eleven Waves transmitted in the same 43 56 57 58 63 66 71 73 78 9.-Combination of two Parallel Vibratory Movements. 0.—Vibrations of Compound Sounds . 1.-Optical Study of Vibratory Movements 2.--Optical Curves representing the Rectangular Vibrations of Two Tuning-forks in Unison 3.—Combination of Two Rectangular Vibratory Movements 86 88 89 90 91 92 93 94 6.-Apparatus for the Comparison of the Vibratory Movements of Two Sonorous Tubes 95 7. Manometric Flames. Fundamental Note, and the Octave above the Fundamental Note . 96 8.-Manometric Flames simultaneously given by Two Tubes at the Octave. 97 FIG. 49.-Manometric Flames of Two Tubes of a Third 50.-Professor Blake's Method of Photographing Vibrations 51.-Curve representing a Sound-wave. 52.-Perronet Thompson's Keyboard 53.-Poole's Keyboard. 54.--Bosanquet's Generalised Keyboard 55.-Plan of Natural Fingerboard . 56.-Organ Stops 57.—The Flute. Longitudinal and Transversal Section the Mouthpiece 58.-Nay or Egyptian Flute 59.-Hautbois. 60. Clarinet . Front and Side View of Reed. 61.-Section of Mouthpiece 62.-Bassoon . 63.-French Horn 64.-Trumpet and Clarion 65.-Trombone 66.-The Human Ear 67.-The Human Voice ON SOUND. INTRODUCTORY. Sound, from a physical point of view, may be defined as Vibration appreciable to the ear. It appears, at its lower limit, to be continuous with vibration as detectable by ordinary tactile sensation; hence its exact musical commencement is rather indefinite. It is usually given at about thirty-two single, or sixteen double vibrations per second. Apparatus for the demonstration of this fact will be noted further on. Its higher limit is even more variable, owing to physiological differences between different ears; but 76,000 single, or 38,000 double vibrations probably represent the highest note ever heard. The line of demarcation between mere noise and musical sound seems similarly vague. Dr. Haughton has ingeniously shown that the rattling of vehicles over equal-sized stones becomes musical at a definite velocity; from the confused rattle of a railway train in a tunnel the practised ear can disentangle, and, as it were mentally sift out, grand organharmonies; and a falling plank in the Crystal Palace gives musical notes by periodic repercussion at equal intervals. On the other side, castanets, tom-toms, side-drums, triangles, cymbals, all instruments of music proper, only give noise, similar to the guns added in Russia to Italian music, or the hundred anvils " played on" at the Boston Celebration. Even Beethoven, in his grandest symphony, sounds every note of the scale at once, with musical effect. Helmholtz lays down the axiom that the sensation of musical sound is caused by rapid and periodic movements of the sonorous body, the sensation of noise by non-periodic movements. B |