to others, which sideward motion combined with gravitation toward centers of attraction, necessarily will originate rotary motions, which again combined with the force of inertia changes the globular nebulæ into spheroids, showing that the simple force of gravitation is sufficient to explain the origin of the planetary motions.

Plateau invented the beautiful experiment of an oil globe balanced in the middle of a mass of alchohol and water, so mixed as to have the same specific gravity; this globe is made to revolve by means of an axis and disk in its centre, it then flattens in the direction of its axis, expands toward its equator, and finally throws off a ring, which, by increasing velocity of its revolution, breaks up in smaller globes, all revolving around the primitive axis and each rotating in an opposite direction on an axis of its As the results of this experiment are of so short a duration that it is impossible for a large audience to observe the important details, I have truthful diagrams made and exhibited here, showing the resultant changes.

own.

This experiment was supposed to illustrate some details of the nebular theory of La Place, namely, the formation of fluid rings from nebular matter, and then breaking up into planets and satelites; but it has done much injury by preventing the right understanding of the cosmogony of the universe. It has, namely, caused the impression that rings were thrown off from the revolving centre, as is the case in this experiment; that the planets were formed by rings thrown off from the sun, the satelites being rings thrown off by the planets, and Saturn was pointed out as an illustration of a planet which had thrown off a ring in the same way as the oil ring, in Plateau's experiment, which ring was not yet broken up into fragments or moons.

Now the impression that rings, moons or planets can possibly be thrown out from a central revolving body, is erroneous, because the supposed similarity between the results of Plateau's experiment and the formations of planetary systems after the nebular theory does not exist. In Plateau's experiment we start with a large fluid ball, held together by nothing but a slight cohesion; this globe is disrupted from the inside by the centrifugal force developed by the rotation of a central solid ball or disk; in the universe we have nebular matter diffused into space, and mutually acting and acted upon by the universal force of gravitation: the reaction produced by this force, commencing from the outside and