HOW SOUND AND WORDS ARE PRODUCED. 49 



points at distances apart corresponding to the length of the wabble- 

 waves ; thus dividing the string into vibrating parts, as in Fig. 6. 



These make their own little swift air- waves, while the whole string 

 is making its large and comparatively slow ones, and thus produce what 

 are called overtones waves within waves. These form the feather-wave 

 trimming spoken of, and shown in Fig. 4. These over-vibrations chord 



g 7 



e" g" W c'" 



:c2: 



5=^: 



:^ 



D 



3 4 



Fig. 7. 



or harmonize with the vibrations of the whole string, and are drowned 

 in it, forming a conglomerate air-wave. They are two, three, four, five, 

 six, seven, eight, etc., times the vibration of the whole string, and it is 

 according to which of these over-vibrations is the fullest, that the 

 sound takes its peculiar quality. Sounds without overtones are dull ; 

 with too many, harsh and grating; and, with the first six in fair propor- 

 tion, are rich and sweet. Fig. 7 represents in musical language the 

 overtones of the note C of 132 vibrations; number 1 being the whole 

 string, the other numbers denoting the overtones up to the eighth, the 

 first six being those that give rich- 

 ness to the tone, and of these, one 

 or another being the most promi- 

 nent according to the source from 

 which the note comes. 



We have said that the over- 

 tones are drowned in the tone 

 only stamping or trimming it, but 

 they can be picked out. Let us see 

 now how we can pick these over- 

 tones out of the conglomerate. 



It is found that a column of air 

 one-fourth the wave-length, of any 

 note's air-waves, will resound to 

 that note and to no other. Let us 

 take our A-fork again with 440 vi- 

 brations per second, making a wave- 

 length of 30 inches, and when vi- 

 brating hold it over a tall jar as in 

 Fig. 8. The column of air may not 

 be the right length. By pouring in water a point will be reached at 

 which the jar will burst into the tone A with the fork. By pouring in 

 more water it stops. A certain length only will resound A. Measur- 



TOL. XIII. 



Fig. 8. 



