ON MUSICAL INSTRUMENTS. 401 



vowels. The perfect consonants may be either explosive, susurrant, or 

 mute; the explosive consonants begin or end with a sound formed in the 

 larynx, the others are either whispers, or mere noises, without any vocal sound. 

 By attending to the various positions of the organ, and by making experi- 

 ments on the effects of pipes of different forms, it is possible to construct 

 a machine which shall imitate very accurately many of the sounds of the 

 human voice; and this has indeed been actually performed by Kratzenstein and 

 by Kempelen. (Plate XXVI. Fig. 359.) 



Although the vibrating ligaments of the glottis may be anatomically 

 denominated membranes, yet their tension is probably confined to the 

 direction of their length, and their action is, therefore, the same with 

 that of a simple string or chord. But in the case of a tambourine and 

 a drum, the membrane is stretched in every direction, and the force of 

 tension consequently acts in a different manner. The principal character 

 of such instruments is their loudness, derived from the magnitude of the sur- 

 face which strikes the air, and the short duration of the sound, on account of 

 the great resistance necessarily produced by the air's reaction. 



Musical instruments which produce sotinds, by means of vibrations depend- 

 ing on the elasticity of solid bodies, are less frequently employed than 

 others; they have a peculiar character of tone, which is by no means 

 unpleasant, but which renders them less fit to be mixed with other instru- 

 ments, since their secondary harmonics are in different proportions. Such is 

 the stacada, a series of cylinders of glass, or of metal, struck either imme- 

 diately with hammers, or by means of keys ; the tuning fork, the gong, the 

 cymbal, and the bell. Bells and other similar instruments are usually made 

 of a mixture of copper, and tin, with a little brass or zinc, which is more highly 

 elastic than either of the component parts taken separately. The harmonica 

 consists of a series of vessels of glass, either placed side by side, or fixed on 

 a common axis, and made to sound by the friction of the fingers, and some- 

 times by that of rubbers of cork. The vibrations of an elastic plate, agi- 

 tated by a current of air, which it continually admits and excludes, con- 

 stitute the sound of the vox humana and regal organ pipes, resembling the 

 human voice as much in their effects as in the mechanism on which they de- 

 pend. (Plate XXVI. Fig 360 . . 36i.) ' . 



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