slips, and incasing them in wood, as in the case of black lead, etc.
In optics, an aggregate or collection of rays of light which converge to, or diverge from, the same point.
PENDANT, in architecture (1) an ornament which is suspended from the roof of a Gothic or Tudor building; the hanging pendants of a vaulted ceiling, uniting solidity with ornament. There are some excellent samples in Henry VI.'s Chapel in Westminster Abbey, London. In vaulted roofs pendants are formed of stone, richly sculptured, and in timber work they are of wood carved. (2) A hanging keystone, the lower face of which projects beyond the intrados of the arch.
In art (in the plural), two pictures, statues, or groups of sculpture or engravings, which, from their similarity of subject, size, form, etc., can be placed together with due regard to symmetry. Nautically: (1) A strap or short rope depending from a mast-head, and having thimbles for bearing the blocks, which transmit the effects of tackles to distant points, etc. Used especially in setting up masts and rigging. (2) A pennant.
PENDLETON, a town of Oregon, the county-seat of Umatilla co. It is on the Umatilla river and on the Oregon Railroad and Navigation Company and the Washington and Columbia River railroads. It is the center and distributing point of an important wheat-growing and cattle-raising regions. Its industries include flour mills, woolen mills, machine shops, etc. Water power is supplied by the river, which is crossed by four bridges. The public buildings include a court house, a public library, a State hospital for the insane, and a Federal building. Pop. (1910) 4,460; (1920) 7,387.
PENDULUM, in mechanics, a simple pendulum is a heavy particle suspended by a fine thread from a fixed point, about which it oscillates without friction. The time of its vibration is directly as the square root of the length, and inversely as the square root of the accelerating force of gravity. The length of the arc through which it vibrates does not affect the result. No simple pendulum can exist; all constructed by man are compound pendulums in which there gravitates, not a particle, but a heavy body called the bob, the law of friction of course operating.
In horology, the ordinary pendulum is believed to have been the invention of Ebn Junius of the University of Cordova, about A. D. 1100, his companion, Gerbert (poisoned in 1102), making the first escapement. Henry de Wyck (1364), Harris (1641), and Huyghens (about 1657), applied it to clocks; Galilei, in 1581, having recommended a pendulous weight as a true measurer, and Sanitorius, in 1612, the combination of a pendulum with wheel work. Pendulums generally move in arcs of circles. In the cycloidal pendulum the rod of suspension describes the arc of a cycloid, and in the conical a cone. Heat lengthens, and cold contracts the rod of a pendulum, if it be of a single metal, as steel or iron. To neutralize these effects compensation pendulums are made; the gridiron pendulum having bars of iron and brass to work against each other, and the mercurial pendulum making the center of the oscillation of the bob uniform by the expansion and contraction of mercury inside. The curved line along which the bob of a pendulum moves is called the arc of vibration, the horizontal chord of that arc the axis of oscillation, and the point around which the pendulum moves the point of suspension, or the center of motion. The length of a pendulum vibrating seconds is directly proportionate to the force of gravity at the place. One constructed to beat seconds at London (lat. of Greenwich Observatory, 51° 28′ N.) at the sea-level must measure 39.13983 inches; at the equator, 39.02074 inches; and at Spitzbergen, 39.21469 inches.
PENELOPE, a celebrated Grecian princess, daughter of Icarius, wife of Ulysses (Odysseus), and mother of Telemachus. According to the Homeric legend, Ulysses, during his long wanderings after the fall of Troy, was generally regarded as dead, and Penelope was vexed by the urgent suits of many lovers, whom she put off on the pretext that she must first weave a shroud for Laertes, her aged father-in-law. To protract the time, she undid by night the portion of the web which she had woven by day. When the suitors had discovered this device, her position became more difficult than before; but fortunately Ulysses returned in time to rescue his chaste spouse from their distasteful importunities.
PENFIELD, EDWARD. American illustrator. He was born in New York in 1866, studying painting first in his native city; then in Holland and England. Returning to the United States he became art editor of “Harper's” in 1891, and designed many magazine covers, posters, calendars, and contributed the illustrations to many stories and articles. His larger decorative work in-
