xii CONTENTS. 



SECTION XV. 



Analysis of the Atmosphere Its pressure Law of Decrease in Density 

 Law of Decrease in Temperature Measurement of Heights by the 

 Barometer Extent of the Atmosphere Barometrical Variations 

 Oscillations Trade-Winds Cloud-Ring Monsoons Rotation of 

 Winds Laws of Hurricanes Page 117 



SECTION XVI. 



Sound Propagation of Sound illustrated by a Field of Standing Corn 

 Nature of Waves Propagation of Sound through the Atmosphere 

 Intensity Noises A Musical Sound Quality Pitch Extent of 

 Human Hearing Velocity of Sound in Air, Water, and Solids 

 Causes of the Obstruction of Sound Law of its Intensity Reflection 

 of Sound Echoes Thunder Refraction of Sound Interference 

 of Sounds . 129 



SECTION XVII. 



Vibration of Musical Strings Harmonic Sounds Nodes Vibration of 

 Air in Wind-instruments Vibration of Solids Vibrating Plates 

 Bells Harmony Sounding Boards Forced Vibrations Resonance 



Speaking Machines 140 



SECTION XVIII. 



Refraction Astronomical Refraction and its Laws Formation of Tables 

 of Refraction Terrestrial Refraction Its Quantity Instances of 

 Extraordinary Refraction Reflection Instances of Extraordinary Re- 

 flection Loss of Light by the Absorbing Power of the Atmosphere 

 Apparent Magnitude of Sun and Moon in the Horizon 153 



SECTION XIX. 



Constitution of Light according to Sir Isaac Newton Absorption of Light 



Colours of Bodies Constitution of Light according to Sir David 

 Brewster New Colours Fraunhofer's Dark Lines Dispersion of 

 Light The Achromatic Telescope Homogeneous Light Accidental 

 and Complementary Colours M. Plateau's Experiments and Theory 

 of Accidental Colours 159 



SECTION XX. 



Interference of Light Undulatory Theory of Light Propagation of 

 Light Newton's Rings Measurement of the Length of the Waves of 

 Light, and of the Frequency of the Vibrations of Ether for each Colour 



Newton's Scale of Colours Diffraction of Light Sir John Her- 

 schel's Theory of the Absorption of Light Refraction and Reflection of 

 Light 167 



