the sun's path, the great circle in which the sun appears to describe his annual course from west to east--really corresponding to the path which the earth describes. The Greeks observed that the eclipses of the sun and moon took place near this circle, whence they called it the ecliptic. The ecliptic has been divided into twelve equal parts, each of which contains 30 deg. (See ZODIAC). The position of the planets and the latitude and longitude of the stars are reckoned by the plane of the ecliptic. The points at which the equator and ecliptic intersect are subject to a continual variation, receding westward at the rate of about 50 seconds a year. The angle at which the ecliptic stands to the equator is also variable, and has been diminishing for about 4000 years at the rate of about 50 seconds in a century. Laplace snowed, however, that this variation has certain fixed limits, and that after a certain time the angle will begin to increase again. The combined result of these two changes is to cause the pole of the earth not to point constantly to the same spot in the heavens, but to describe an undulating circle round a certain point. This movement, however, is so slow that it takes many thousand years to complete it.