Thus the planet Neptune would be left behind in the first sun-ring, to make its one moon; the planet Uranus left in the next sun-ring; and so on down to Mercury. The outer planets would cool off first, become habitable, and, as the sun contracted and they radiated their own heat, become refrigerated and left behind by the retreating sun. The four great classes of facts confirmatory of this hypothesis are as follows: 1st. All the planets move in the same direction and nearly in the same plane, as if thrown off from one equator; 2d. The motions of the satellites about their primaries are mostly in the same direction as that of their primaries about the sun; 3d. The rotation of most of these bodies on their axes, and also of the sun, is in the same direction as the motion of the planets about the sun; 4th. The orbits of the planets, excluding asteroids, and their satellites, have but a comparatively small eccentricity; 5th. Certain nebulae are observable which are not yet condensed into solids, but are still bright gas.”[1] The nebular hypothesis above stated was advanced by astronomers early in the eighteenth century, and later established by Laplace on a mathematical basis, who at the same time advocated the theory as materialistic. It is accepted quite generally by astronomers at the present day, though in a greatly modified form; for there are many difficulties in the way of a full belief of the theory. Sir Robert Ball in a late work says of Herschel’s belief of the transmutation of nebulae into stars; “To establish this theory it would be necessary to watch the actual condensation of one single nebula from the primitive gaseous condition down to the stellar points. It may easily be conceived that such a process would require a vast lapse of time, perhaps enormously greater than the period between the invention of the telescope and the present moment. It may at all events be confidently asserted that this condensation of a nebula into a star is a process which has never been witnessed.” Concerning the theory of Laplace he tells us that it is “almost incapable of receiving any direct testimony;” and gives as the verdict of science, the words of Newcomb; “At the present time the nebular hypothesis is only indicated by the general tendencies of the laws of nature.”