REVOLUTION, a fundamental change in government, or in the political con stitution of a country, effected suddenly and violently, and mainly brought about by internal causes; a revolt against the constituted authority successfully and completely accomplished. In most revo lutions there are three turns of the wheel. First there is a moderate move ment forward, then, after a time, a second forward movement. The extreme party who now come into power create a reaction against the revolution, and the wheel moves backward. In the great French Revolution first there were the Girondists, then the Jacobins, then the reaction to monarchy under the first Napoleon, and in due time again to the Bourbons. In the United States the term Revolution is applied specifically to the American War for Independence, which began in 1775 with the irregular running fight popularly known as the battle of Lexington, and practically ended with the surrender of Lord Corn wallis, at Yorktown, Va., to the com bined forces of the French and Ameri cans, in the year 1781. The English Revolution was that revolution in Eng land by which James II. was driven from the throne in 1688. The Russian Revolution was that of 1917 which led to the triumph of the Bolsheviki over the moderates, and the development of So viet power. The German Revolution was
that of 1918, by which the German Em peror and the kings and other reigning princes of the various sovereign Ger man states were driven from their thrones.
In astronomy: (1) The motion of a planet around the sun, or of a around a planet. The point to which it returns is called annual, anomalistic, nodical, sidereal, or tropical, according as it has a relation to the year, the anom aly, the nodes, the stars, or the tropics. (2) See ROTATION. In geometry, when one line moves about a straight line, called the axis, in such a manner that every point of the moving line generates a circumference of a circle, whose plane is perpendicular to the axis, that motion is called revolution, and the surface is called the surface of revolution. Every plane through the axis is called a merid ian plane, and the section which this plane cuts from the surface is called a meridian curve. Every surface of revolution can be generated by revolv ing one of its meridian curves about the axis. The revolution of an ellipse round its axis generates an ellipsoid; the revolution of a semicircle round the diameter generates a sphere; such solids are called solids of revolution.