With regard to the fall towards Venus and final rise towards Mercury, we have to take into consideration the anomalies--already taken notice of--in the dimensions, densities, etc. etc., of the two planets Earth and Venus; it being, we may confidently say, certain that the whole of them have arisen from the same causes. Following up the idea of a dumb-bell nebula--as we might have done in the case of Jupiter also--as the breadth of space for receiving matter abandoned by the nebula went on rapidly decreasing, the thickness of the ring left behind would go on increasing, and the overhanging matter of the dumb-bell would be deposited always in greater quantity on the outer than the inner part of the ring as it broadened; we can conceive that the whole extent of the sheet of matter allotted to the Earth and Venus would be thicker at the outer than the inner part. Hence, when this part of the sheet came to be divided into two parts for the formation of two planets, the outer would naturally be the greater and denser of the two, and thus occasion the rise in density from Mars to the Earth, and the fall to Venus. Finally the rise in density to Mercury would be only the beginning of the gradual, and final, rise to the sun as it is at present. If the idea of a nebula in the form of a cylinder with hemispherical ends is admitted as possible, or somewhat like a dumb-bell, the extreme diameters of the 9 successive nebulæ we have dealt with would be considerably different in their equatorial directions to what we have given them, although their polar diameters might continue to be not far from the same; but that would have very little effect on the operations we have gone through, seeing we have shown that there could be no actual divisions between them such as we have adopted; and that the division of the sheet of matter abandoned into separate rings must have been brought about by some means which we cannot explain; a process, nevertheless, which has been subject to some law, or laws, operating evidently in a regular and steady manner throughout the whole time, during which the matter was being abandoned, as is proved by the general uniformity, or harmony, in the distances of the planets from the sun. Should anyone come to be able to account for the division of this sheet of matter into distinct and separate rings, he will also be able to account for the acceleration of rate of revolution from one planet to another, and for the anomalous rates in the cases of the Earth and Venus.