Ellipsoids

Ellipsoids are of two kinds, the simpler being those of revolution, produced by an ellipse turning round the major or the minor axis. The surfaces so generated are known as prolate and oblate spheroids respectively, and our globe is a well-known instance of the latter. The ellipsoid proper has three rectangular axes of different lengths, and its section in any direction is an ellipse, whereas the spheroids must give a circular section if cut at right angles to the axis of revolution.