THEORY OF THE JEW’S HARP.
If you cause the tongue of this little instrument to vibrate, it will produce a very low sound; but, if you place it before a cavity, (as the mouth,) containing a column of air, which vibrates much faster, but in the proportion of any simple multiple, it will then produce other higher sounds, dependent upon the reciprocation of that portion of the air. Now, the bulk of air in the mouth can be altered in its form, size, and other circumstances, so as to produce by reciprocation, many different sounds; and these are the sounds belonging to the Jew’s Harp.
A proof of this fact has been given by Mr. Eulenstein, who fitted into a long metallic tube a piston, which, being moved, could be made to lengthen or shorten the efficient column of air within at pleasure. A Jew’s Harp was then so fixed that it could be made to vibrate before the mouth of the tube, and it was found that the column of air produced a series of sounds, according as it was lengthened or shortened; a sound being produced whenever the length of the column was such that its vibrations were a multiple of those of the Jew’s Harp.