Molecular exchange, resistance, and its collecting power, may have rendered its orbit circular, and have brought it into the plane of the planet's rotation. There seem no strong reasons, such as irregularity, etc., why Proctor's theory might not account for the formation of the moons. Another objection to this theory is the fact that there are comparatively few small bodies still travelling the system. There are, of course, a countless number of such bodies, but not so many as might be expected. The nebula would cause the bulk of the small bodies, except moons, to be absorbed into the sun; and the same action may have cleared the space about the planets of all matter except the satellites. The motion of the sun and its system in space may be accounted for in so many different ways, and does not appear to offer any difficulties to any theory, that I shall not discuss it. Recapitulation. I recapitulate the more important of the points in what at present seems the most probable origin of the solar system. Two rare bodies, moving with considerable velocity, rotating, and having revolving around them in all planes a large number of bodies, some of a large size, come within each others attraction, are brought together by gravitation, and come into tangential collision. During the collision most of the accompanying bodies fly off in directions which are approximately in one plane; the component of the motion not in the plane being due to their original orbital rotation. The new orbit of all the bodies tends to be highly eccentric, but the general mass expands, and by its agency the orbit becomes nearly circular. Among the vast number of bodies thrown off during impact, the larger gradually collect the lesser up, also much of the matter that coalesces from the nebula, and many heavy molecules. Where this action is very considerable, the original mass forms so small a fraction of the final planet, that its original irregular motion almost disappears, and its axis is almost rendered perpendicular. The nebular resistance will tend to lessen the distance of the smaller bodies, and convert them into zodiacal light, or absorb them entirely into the sun, except the moons, which cannot escape the planet's attraction. All the smaller planets and those nearer the sun are robbed of their lighter molecules, and become very dense compared to the general mass of the system, but, as the nebulæ contract within their orbit, they again pick up the lighter molecules which become the atmosphere.