xii CONTENTS. 



CHAPTER XVIII. 



THE PROBABLE ORIGIN AND AGE OF THE SUN's HEAT. 



Continued. 



PAGE 



Not obliged to assume that Gravitation is the only Source of the 

 Sun's Heat. — How the Mass obtained its Temperature. — No 

 Limit to the Amount of Heat which may have been pro- 

 duced. — Age of the Sun in Relation to Evolution. — Note 

 on Sir William Thomson's Arguments for the Age of the 

 Earth, 282 



CHAPTER XIX. 



THE PROBABLE ORIGIN OF NEBULiE. 



Motion in space as a source of heat. — Reason why nebulae occupy 

 so much space. — Reason why nebulae are of such various 

 shapes. — Reason why nebulae emit such feeble light. — Heat 

 and light of nebulae cannot result from condensation. — The 

 gaseous state the first condition of a nebula. — Star -clusters. 

 — Objections considered. . ... . . . . 297 



Index 316 



Chart of Probable Path of the Ice in North-Western Europe 

 To face page 133. 





