SEVERAL important facts concerning sound must have been known at a very early period. The tuning of the lyre, and various other instruments, which are coeval with the remotest antiquity, necessarily implies an ac quaintance with the fact, that as we diminish the length of musical strings, or increase their tension, we render their tone more acute. We have, however, no reason to bulinT, that till 5)0 years before the Christian cra, aity attempt had been made to discover the relation which subsists between the length of strings producing the various notes of tousle. About this period, Pytha goras gave a correct determination of the ratios between S ItriOLL, SOUIRIN.
Tile account which the ancients give of the mode by which tin c philosopher discovered these values is evi dently fabulous, so that we cannot say with certainty how he obtained them ; though it was probably by means of some instrument, which, like the monochord, would enable him to increase or diminish at pleasure the effective of a About 200 years subsequent to the time of Pythago ras, Aristotle, who seems to have attended to almost every subject, wrote upon the nature of sound. He understood, that the number of vibrations performed by strings, or by the air in pipes, is inversely as their lengths ; and that sound is transmitted to the ear by similar vibrations communicated to the atmosphere. We arc not informed on what evidence Aristotle found ed these doctrines ; but it is likely, from the loose reasoning, and imperfect analogies with which the an cients were satisfied in their physical inquiries, that these opinions were merely sagacious conjectures.
Such, in Acoustics, was the narrow patrimony trans mitted to us by the ancients ; and even this scanty pit tance see did not receive till it was too late to be of any material advantage. During the darkness which over spread the it hole literary world, no additions were made to the science of Acoustics, and even the knowledge which the ancients possessed on this subject, was in a great measure lost ; for though the writings of Aristotle had been preserved, they were so completely misunder stood, as to be of no use. Galileo may therefore be justly said to have (about the year 1600 after Christ) disco ve red anew, what was known to the ancients concerning the nature of sound. lie conceived, that sound is me?e
ly a vibration of the air ; that the distinction between musical sounds probably consists in the different fre quency of these vibrations ; and that a musical string, by performing each of its vibrations in equal times, pre serves its uniformity of tone. Ile considered the whole matter of it musical string as if collected into its middle point ; and demonstrated, that on this supposition its vibrations would be performed in equal times ; whence he concluded, that if the matter be diffused uniformly along the string, its vibrations will obey the same law.
Though the latter part of this reasoning, in which it is inferred that an uniform string vibrates similarly to what it would do if its whole matter were collected into one point, proceeds on an analogy too distant to be by any means conclusive, the labours of Galileo were va luable, as they led the way to more accurate investiga tions.
In the year 1714, Dr Brook Taylor demonstrated Ga lileo's theorem, upon the hypothesis of the initial form of a vibrating string being what is called an harmonic curve ; and he gave a determination of the frequency of vibration in such a curve. By this demonstration, Dr Taylor has an indisputable claim to the honour of being the first who proved the kochronisin of a vibrat ing string. M. Sauveur had indeed, in the preceding year, attempted to give a solution of the same theorem, nit his demonstration is in all respects erroneous. Dr Taylor was mistaken in supposing, that, whatever may be the initial form of an inflected string, it will, alter a few vibrations, assume the form of an harmonic curve ; and that this is the only curve in which isochronous vibrations can be performed, or all the points of a string arrive at its axis at the same time. Yet his determina tion of the frequency of the vibrations of a string ex tends to all cases ; as this frequency is the same, what ever be the initial figure of the string, if it be all situ ated on the same side of its axis.