Sound. 377 



marry articles that would hardly be classed as musical instruments, or 

 even be thought to have any music in them, will often be found to join 

 in when their note is sounded, showing that they are possessed of a 

 susceptibility to some sort of vibratory impulse, however they are put 

 together. Everyone has observed how piano strings, and other deli- 

 cately adjusted instruments, can be vibrated by the voice, when uttered 

 in the pitch of the string. This is simply the communication of the 

 proper vibration from the voice to the air and from the air to the string. 

 Certain tones of a large church organ will often cause the vibration of 

 some part of the building or its furniture as the windows, or chande- 

 liers, or even the pews, and sometimes the people. Whenever any ob- 

 ject trembles in response to a musical note it is evidence that it has a 

 more or less perfectly developed fundamental tone. What the tone is 

 depends on its material, its shape, state of molecular tension, &c. 

 Bodies of irregular shape and uneven tension have more than one fun- 

 damental^ different parts giving different sounds. When a shock to 

 such a body sets all its tones in vibration at once, the result is a crash 

 of discordant noises as in a gong. But after two sounds are compared 

 and found to agree as to length and amplitude of vibration, or pitch 

 and loudness, there may still be a great difference between them. Let 

 a flute, a violin, and a human voice all sound the same note at once, 

 and though they harmonize perfectly it is easy to pick out each by its 

 peculiarities. This individuality of sounds is called their timbre. It is 

 scientifically proved that almost all sounds are composite and are made 

 up of vibrations of different lengths or pitch in simultaneous action. 

 When a violin string is vibrated as a whole, the result is the funda- 

 mental tone of the string ; but beside the great vibration, the string 

 divides itself into several parts, each of which sets up a sub-vibration of 

 its own. It may divide into any number of equal parts, from two to 

 seven. When it is divided into two the sub-divisions make two vibra- 

 tions for every one of the whole string, thus giving the octave of the 

 fundamental, as well as the fundamental itself. These additional or 

 super-added tones are called the harmonics. As stated above, the C of 

 the small octave is formed by 132 vibrations. Its possible harmonics 

 are those only whose vibrations are multiples of 132. The first is the 

 C of the second octave with 264 vibrations, the next is Gr of second oc- 

 tave 396 vibrations, then C of third octave 528 vibrations, E 660 vibra- 

 tions, Gr 792, and lastly, the seventh harmonic having 924 vibrations 

 with no representative note in our musical scale. Take the F string as 

 another example, as follows : F' with 176 vibrations, F" 352, C 528, 

 F' ' ' 704, A 880, C 1056, 7th harmonic 1232 with no corresponding 

 letter. The human voice is rich in harmonics, and the peculiar timbre 

 and individuality of each voice is due to the variety of the harmonics 



