Page:The evolution of worlds - Lowell.djvu/146

114 the eclipsed Sun, only comes out to view when the obliterating brightness of the main body of the rings is withdrawn by their edgewise presentation.

The reason the out-of-plane particles are most numerous just inside the point of disturbance is not only that there the action throwing them out is most violent, but that all the time a levelling action quite apart from disturbance is all the time tending to reduce them again to one plane, as we shall see further on when we come to the mechanical forces at work. Thus the tore is most pronounced on its outer edge, and falls to a uniform level at its inner boundary. The effect is somewhat as represented in the adjoining cut, in which the vertical scale is greatly magnified:—

With Saturn ended the bounds of the solar system as known to the civilized world until 1781. On March 13 of that year Sir William Herschel in one of his telescopic voyages through space came upon a strange object which he at once saw was not a star, because of its very perceptible round disk, and which he therefore took for a