CONTENTS. 



CHAPTER I. 



PAGE. 

 The Constitution of Nature 1 



CHAPTER II. 

 Radiation 20 



CHAPTER III. 



On Radiant Heat in Relation to the Color and Chemical Constitu- 

 tion of Bodies 54 



CHAPTER IV. 

 New Chemical Reactions Produced by Light 71 



CHAPTER V. 

 TheSky 98 



CHAPTER VI. 

 Voyage to Algeria to Observe the Eclipse 107 



CHAPTER VII. 

 Niagara 132 



CHAPTER VIII. 

 The Parallel Roads of Glen Roy 155 



CHAPTER IX. 

 Alpine Sculpture ' 175 



CHAPTER X. 

 Recent Experiments on Fog-Signals 193 



CHAPTER XL 

 On the Study of Physics 215 



