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 CHAPTER XVIII. Return to the peaks abandoned by the original nebula. An idea of their number 319 Example of their dimensions. What was made out of them 320 What could be made from one of them 321 How it could be divided into comets and meteor swarms 322 An example given. How a comet may rotate on its axis. And what might be explained thereby. Orbits and periods of revolution 323 Not ejected from planets. Their true origin 324 Study of the velocities in orbit of comets, and results thereof 326 How far comets may wander from the sun and return again 327 No reason why comets should wander from one sun to another. Confirmatory of the description, in Chapter XV. of the sun's domains 328 Of the eternal evolution and involution of matter. The atmosphere and corona of the sun 329 Partial analogy between it and the earth's atmosphere 331 The density of it near the sun's surface cannot be normally less than 28 atmospheres, but might be so partially and accidentally 332 Probable causes of the enormous height of its atmosphere 332 The mass taken into account, but cannot be valued 334 Most probably no matter in the sun exceeds half the density of water. The unknown line in the spectrum of the corona belongs to the ether 335 NEW THEORIES IN ASTRONOMY. INTRODUCTION.