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 The behaviour of heat produced in the nebula, and its power 313 How sun-spots are produced 314 Cyclonic motions observed in sun-spots. Why not all in certain directions, and why only observed in a very few 315 Cyclonic motions in prominences treated of 316 Many other things might be explained, on some of which we do not dare to venture. Concluding observations 317