dividing itself by 2 or 3 or 5, etc., up through the whole geometrical series of numbers, not keeping fixed at one thing; but while the whole length is vibrating the fundamental partial, it keeps shifting the still nodes along its length, and sometimes longer and sometimes shorter segments are sounding the other partials which clothe the chief sound. It has been commonly said that "a musical sound is composed of three sounds," for every ear is capable of hearing these three, and with a little attention a few more than these; but many will be startled when told that there are twenty-five sounds in that sound. Eighteen of them are simply the octaves of the other seven, all of these seven except one having one or more octaves in the sound. Four of the seven also are very feeble, the one which has no octave being the feeblest of all. Two of the other three are so distinctly audible along with the chief partial that they gave rise to the saying we have quoted about a musical sound being composed of three sounds.1 If the three most pronounced partials were equally developed in one sound, it could not be called one sound - it would decidedly be a chord; and when in the system they do become developed, they form a chord; but in the one sound they, the partials, having fewer and fewer octaves to strengthen them, fade away in the perspective of sound. The sharp seventh, which in the developed system has only one place, not coming into existence until the sixth octave of the genesis, is by far the feeblest of all the partials, and Nature did well to appoint it so. These harmonics are also sometimes called "overtones," because they are higher than the fundamental one, which is the sound among the sounds, as the Bible is the book among books.
Guiseppe Tartini, 200 years ago, while practicing on his violin, observed a very interesting phenomenon in music in the matter of notes or sounds,
1 Speaking of acute harmonics Pole says - "The first six are the only ones usually considered to be of any practical importance, and it is rarely possible to distinguish more than 10 or 12."
Mercenne (French, 1636) says - "Every string produces 5 or more sounds at the same instant, the strongest of which is called the natural sound of the string, and alone is accustomed to be taken notice of; for the others are so feeble that they are only perceptible to delicate ears . . . not only the octave and fifteenth, but also the twelfth and major seventeenth are always heard; and over and above these I have perceived the twenty-third and ninth partial tones in the dying away of the natural sound."