The sun's neighbours still exercise their attraction over him 282 Regions of greatest density in the 9 nebulæ dealt with; compared with the orbits of the planets made from them 283 Results of comparison favourable to the theory 287 Differences of size in the planets have arisen from variations in the quantity of matter accumulating on the nebulæ 289 Causes of the retrograde motions in Neptune, Uranus, and their satellites 290 Probable causes of the anomalous position of Neptune 292 Rises and falls in the densities and dimensions of the planets explained 293 The form of the nebulæ must have resembled a dumb-bell 295 More about rises and falls in densities 296 Reason why the Asteroid nebula was the least dense of the system 297 Not necessary to revise the dimensions given to the 9 nebulæ 298 Causes of the anomalies in the dimensions, densities, etc., of the Earth and Venus 299 The strictly spherical form of the sun accounted for. But it may yet be varied 299 Repetition that a spherical body could not be made from a lens-shaped nebula by attraction and condensation 300 CHAPTER XVII. Former compromises taken up and begun to be fulfilled 301 Estimates of the heat-power of the sun made only from gravitation hitherto 302 Contraction and condensation of a nebula solid to the centre. Heat produced from attraction as well as by gravitation 303 What quantity of heat is produced by a stone falling upon the earth 304 Showing again that there is a difference between attraction and gravitation 305 Contraction and condensation of a hollow-sphere nebula, in the same manner as the solid one 305 Differences of rotation would be greater in a hollow nebula; because a great deal of the matter would be almost motionless in a solid sphere 306 In neither case could matter be brought to rest, but only retarded in motion. Different periods of rotation accounted for 307 Table of different rates explained 309 Heat produced by gravitation, attraction and churning, not all constituents of the heat-power of the sun 310 There can be no matter in the sun so dense as water 311 The hollow part of the sun acting as a reservoir of gases, heat and pressure 312