518 



NEXT we come to the Vibrator, sometimes called the Heed. 

 It is introduced into various musical instruments, such, for 

 example, as the harmonium, the clarionet, the ohoe, the 

 bassoon, and various organ pipes. 



The simplest form of the Vibrator is shown in the Jew's 

 Harp, as it is popularly called, though it is not a harp, and 

 has nothing to do with Jews. 



The word is really a mistaken pronunciation of " jaw's 

 harp," because the instrument is held against the teeth, while 

 its tongue is vibrated by strokes of the finger. These vibra- 

 tions affect the air within the mouth, and, by expanding or 

 contracting the mouth, the sound is lowered or raised according 

 to the laws of Acoustics. Of course, the range of notes is very 

 small, being limited to those of the common chord, and even 

 they being attainable only by a practised performer. Very 

 good effects, however, have been produced by means of a series 



VIBRATING STRINGS. JEOLIAN HARP. 



of Jew's Harps, set to different tones by loading the end of the 

 tongue with sealing-wax or similar substances. 



AN apparatus constructed on the same principle is to be 

 found in the vocal organs of the male Cicada. If one of these 

 insects be examined on the lower surface, two curious and 

 nearly circular flaps will be seen, just at the junction of the 

 thorax with the abdomen. It is by the action of these two little 

 vibrators that the insect is able to produce a sound so loud, 

 that in calm weather it may be heard at the distance of a 

 mile. 



THE accompanying illustration is, in fact/ a sort of chart as to 

 the vibration of sound. 



On the right is shown the ^Eoi.iAN HAEP, with its upper lid 

 raised, so as to show the structure of the strings. These are all 



