ACOUSTICS.
CHAPTER I.
PERCUSSION.—THE STRING AND REED.—THE TRUMPET.—EAR-TRUMPET.—STETHOSCOPE.
The Science of Sound.—Rhythmical Vibrations.—The Drum.—Primitive Drums.—The Solid and Hollow Log.—The Bass Drum and Kettle-drum.—African Drums.—Gnostic Gems and the Ashanti Drum.—Tympanum, or Drum of the Human Ear, and its Mechanism.—An artificial Tympanum.—The String.—The Bow and the Harp.—The Harpsichord and the Zither.—The Bow and the Violin.—The Cricket.—The Vibrator, or Reed.—The Jew’s Harp and Harmonium.—The Cicada and its Song.—Harmonics upon Strings.—The Æolian Harp.—Harmonics upon the Trumpet.—The Trombone.—Trachea of the Swan.—The Ear-trumpet.—The Sea-shell.—The Stethoscope.—Savage Food.—The Aye-aye.—The Siren and its Uses.—Echo and Whispering Gallery.
IN a work of this nature it would be absolutely impossible, not to say out of place, to give an account of so elaborate a subject as Acoustics, i.e. the science of Sound. Suffice it to say, that all sounds are produced by the vibration of air, and that the fewer vibrations, the lower is the sound, and vice versâ.
When such vibrations are produced regularly, they form Musical sounds, but, if irregularly, the sounds can be only distinguished under the term of Noise. The earliest germ of music lies in certain savage races, who, as long as they can maintain a rhythmical beat on any resonant substance, do not particularly care what it is. A hollow tree is a splendid instrument in their opinion, but, if this cannot be had, a dry log of wood will answer the same purpose.
Some tribes, more ingenious than others, cut a deep groove upon the upper surface of a log, hollow it through this groove, and then hammer away at it to their hearts’ content. The next move was to cut off a section of the trunk of a tree, hollow it, set it on end, and then beat it on the sides.
Lastly, some one hit upon the idea that if the open upper part of the hollowed log were covered with a tightly stretched membrane, and that if the membrane, instead of the log, were beaten, the resonance would be increased. In consequence, the real Drum was invented, and seems to have existed from time immemorial in parts of the world so distant that they could not have had any communication with each other.
Take, for example, the well-known “Bass Drum” of our bands, which is shown on the right hand of the figure. We make it a very ornamental article, with frame of metal, and heraldic decorations of all kinds.
Lying against it is one of a pair of Kettle-drums, such as are always seen in mounted bands. They look very easy to play, but, if the reader will try a pair, he will soon find his mistake.
But there are savage tribes of Western Africa who make Drums of such wonderful power that their sullen roar is heard for miles around, as their slow, triple beat summons the tribe to arms like the fiery cross of the Highland clans. As to shape, lightness, and beauty, our Drums are infinitely superior to theirs, but, so far as I can gather from personal and written narratives of African travellers, none of our Drums surpass theirs in richness, depth of tone, and power of carrying sound.