2 CONTENTS 



ICE AND GLACIERS 



PAGE 



A LECTURE DELIVERED AT FRANKFORT-ON-THE-MAIN, AND 

 AT HEIDELBERG, IN FEBRUARY, 1865 221 



THE WAVE THEORY OF LIGHT 



[A LECTURE DELIVERED AT THE ACADEMY OF Music, PHILA- 

 DELPHIA, UNDER THE AUSPICES OF THE FRANKLIN 

 INSTITUTE, SEPTEMBER 2QTH, 1884] 263 



THE TIDES 



[EVENING LECTURE TO THE BRITISH ASSOCIATION AT THE 

 SOUTHAMPTON MEETING, FRIDAY, AUGUST 25-TH, 1882] . 287 



THE EXTENT OF THE UNIVERSE 325 



GEOGRAPHICAL EVOLUTION 339 



