STRING

, in Music. See Chord.

If two Strings or chords of a musical instrument only differ in length; their tones, or the number of vibrations they make in the same time, are in the inverse ratio of their lengths. If they differ only in thickness, their tones are in the inverse ratio of their diameters.

As to the tension of Strings, to measure it regularly, they must be conceived stretched or drawn by weights; and then, cæteris paribus, the tones of two Strings are in a direct ratio of the square roots of the weights that stretch them; that is, ex. gr. the tone of a String stretched by a weight 4, is an octave above the tone of a String stretched by the weight <*>.

It is an observation of very old standing, that if a viol or lute-string be touched with the bow, or the hand, another String on the same instrument, or even on another, not far from it, if in unison with it, or in octave, or the like, will at the same time tremble of | its own accord. But it is now found, that it is not the whole of that other String that thus trembles, but only the parts, severally, according as they are unisons to the whole, or the parts, of the String so struck. Thus, supposing AB to be an upper octave to ab, and therefore an unison to each half of it, stopped at c; if while ab is open, AB be struck, the two halves of this other, that is, ac, and cb, will both tremble; but the middle point will be at rest; as will be easily perceived, by wrapping a bit of paper lightly about the string ab, and moving it successively from one end of the string to the other. In like manner, if AB were an upper 12th to ab, and consequently an unison to its three parts ad, de, eb; then, ab being open, if AB be struck, the three parts of the other, ad, de, eb will severally tremble; but the points d and e remain at rest.

This, Dr. Wallis tells us, was first discovered by Mr. William Noble of Merton college; and after him by Mr. T. Pigot of Wadham college, without knowing that Mr. Noble had observed it before. To which may be added, that M. Sauveur, long afterwards, proposed it to the Royal Academy at Paris, as his own discovery, which in reality it might be; but upon his being informed, by some of the members then present, that Dr. Wallis had published it before, he immediately resigned all the honour of it. Philos. Trans. Abridg. vol. I, pa. 606.