A farther use of the pendulum is in furnishing a general and unperishing standard of measure. This application is suggested in the third volume of the 'Reflections' of Mersenne, published in 1647, where he observes that it may be best for the future not to divide time into hours, minutes, and seconds, but to express its parts by the number of vibrations of a pendulum of given length, swinging through a given arc. It was soon seen that it would be more convenient to invert this process, and to choose as an unit of length the pendulum which should make a certain number of vibrations in the unit of time, naturally determined by the revolution of the earth on its axis. Our Royal Society took an active part in these experiments, which seem, notwithstanding their utility, to have met from the first with much of the same ridicule which was lavished upon them by the ignorant, when recently repeated for the same purpose. "I contend," says Graunt[168] in a dedication to the Royal Society, dated 1662, "against the envious schismatics of your society (who think you do nothing unless you presently transmute metals, make butter and cheese without milk, and, as their own ballad hath it, make leather without hides), by asserting the usefulness of even all your preparatory and luciferous experiments, being not the ceremonies, but the substance and principles of useful arts. For I find in trade the want of an universal measure, and have heard musicians wrangle about the just and uniform keeping of time in their consorts, and therefore cannot with patience hear that your labours about vibrations, eminently conducing to both, should be slighted, nor your pendula called swing-swangs with scorn."[169] FOOTNOTES: [153] One of the Commissioners was the father of Blaise Pascal. [154] These instruments were very inferior to those now in use under the same name. See "Treatise on Opt. Instrum." [155] Theoricæ Mediceorum Planetarum, Florentiæ, 1666. [156] Circulus affixus virgæ paletorum qui cum eâ de vi movetur. [157] Utriusque Cosmi Historia. Oppenhemii, 1617. [158] Huygenii Opera. Lugduni, 1724. [159] Mémoires de l'Academie, 1717. [160] See page 84. [161] De nova Temporis dimetiendi ratione. Londini, 1680. [162] Storia della Lett. Ital. [163] Museum Mazuchellianum, vol. ii. Tab. cvii. p. 29. [164] Almagestum Novum, vol. i. [165] Quovis horologio accuratius. [166] Clarorum Belgarum ad Ant. Magliabech. Epistolæ. Florence, 1745, tom. i. p. 235. [167] Kepleri Epistolæ. [168] Natural and Political Observations. London, 1665. [169] See also Hudibras, Part II. Cant. III. They're guilty by their own confessions Of felony, and at the Sessions Upon the bench I will so handle 'em, That the vibration of this pendulum Shall make all taylors' yards of one Unanimous opinion; A thing he long has vaunted of, But now shall make it out of proof.