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EQUATOR. By the celestial equator is Understood that imaginary great circle in the heavens, the plane of which is perpendicular to the axis of the earth; it is syervwhere 90° distant from the poles of the earth,, which are therefore its poles, and its axis is the axis of the earth. It divides the celestial sphere into the northern and southern hemispheres. During his apparent yearly course, the sun is twice in the equator, at the beginning of spring and of autumn. (See Equinox, and Day.) Then the day and night are equal,whence the name of equator The situation of the stars, with respect to the equator, is determined by their declension and right ascension, (q. v.) The equator, or equinoctial, called by mariners simply the line, is that great circle of our globe, every point of which is 90 degrees from the poles, which are also its poles, and its axis is the axis of the earth. It is in the plane of the celestial equator. All places which are on it, have invariably equal days and nights. (See Day.) Oui earth is divided by it into the northern and southern hemispheres. The diur nal revolution of the earth is in the di rection of it. It crosses the centre of Africa, the islands of Sumatra, Borneo Celebes, &c, in Asia, then traverses the Pacific ocean, and crosses South Ameri.ca, in Colombia, thence proceeds through. the Atlantic back to Africa. To crosv the line, in navigation, is to pass over the equator. The equatorial regions are subject to long calms, alternating with frightful hurricanes. As equal or mean time is estimated by the passage of arcs of tiie equator over the meridian, it frequently becomes necessary to convert parts of the equator into time, and the converse, which is performed by the following analogy, viz.as 15° : 1 hour : : nny arc of the equator : the time it has been in passing. Or, conversely, 1 hour : 15° : : any given time : to the arc of the equator.From this circle is reckoned the latitude of places, both north and south, in degrees of the meridian. (See Latitude, and Longitude.)