ARBUTUS, a genus of plants belong ing to the order of ericacen (heath worts). A species, the A. unedo, or austere strawberry tree, is found, ap parently wild, in the neighborhood of the Lakes of Killarney. It has panicles of large, pale greenish-white flowers and red fruit, which, with the evergreen leaves, are especially beautiful in the months of October and November. Trail ing arbutus is a creeping or trailing plant (epigtea repens) with rose-colored blos soms, found chiefly in New England in the spring. Commonly called May flower, or sometimes ground laurel.
ARC, in geometry, a portion of the circumference of a circle, cut off by two lines which meet or intersect it. Its mag nitude is stated in degrees, minutes, and seconds, which are equal to thos3 of the angle which it subtends. Hence, counted by degrees, minutes, and seconds, the arc of elevation and the angle of elevation of a heavenly body are the same, and the two terms may be used in most cases in differently. The straight line uniting the two extremities of an arc is called its chord. Equal arcs must come from circles of equal magnitude, and each must con tain the same number of degrees, minutes, and seconds as the others. Similar arcs
must also each have the same number of degrees, minutes, and seconds, but they belong to circles of unequal magnitude. Concentric arcs are arcs having the same center.
In mathematical geography, an arc of the earth's meridian, or a meridional arc, is an arc partly measured on the surface of the earth from N. to S., partly cal culated by trigonometry. Such arcs have been measured in Lapland; in Peru; from Dunkirk, in France, to Barcelona, in Spain; at the Cape of Good Hope, and from Shanklin Down, in the Isle of Wight, to Balta, in Shetland. It was by these measurements that the earth was dis covered to be an oblate spheroid.
In electricity, a voltaic arc is a lumi nous arc, which extends from one pencil of charcoal to another when these are fixed to the terminals of a battery in such a position that their extremities are one-tenth of an inch apart.