CONTENTS Xi 



CHAPTER IX. 



Light and Sound 150 



Luminous Bodies. Transparent and Opaque Bodies. Light and 

 Its Properties. Images through Small Openings. Shadows. 

 Brightness or Intensity of Light. Candle Power. Exercises. 

 Division of Light Striking a Body. Reflection of Light. Mirrors. 

 Dispersed or Diffused Light. Refraction of Light. The Lens. 

 Composition of White Light. The Rainbow. Absorption of Light; 

 Color. The Sky and Its Colors. Change of Light into Heat. 

 Light and Life. Exercises. Simple Microscope. Compound Mi- 

 croscope. The Camera. How Sounds are Made and Carried. 

 Sound Waves. Echoes. Noise and Tone. The Telephone. 

 Summary. Exercises. 



CHAPTER X. 



Simple Machines 174 



Need of Machines. Law of Machines. The Lever. Classes of 

 Levers. Exercises. Pulleys. Wheel and Axle. Inclined Plane. 

 -The Wedge. The Screw. Friction. Sailboat. The Kite 

 The Airship. The Windmill. Summary. Exercises. 



CHAPTER XI. 



Acids, Alkalies, and Cleaning 188 



Acids. Classes of Acids. Acids and Coloring Matter. Action 

 of Acids with Metals. Action of Acids with Carbonates. Alkalies 

 or Bases. Caustic Soda and Caustic Potash. Neutralization; 

 Salts. Tests for Certain Salts. Exercises. The Washing of Cloth- 

 ing. Soap and Soap Making. Action of Soap. Soap and Hard 

 Water. Materials of Clothing. Dyes. Paints. Removal of 

 Stains. Summary. Exercises. 



CHAPTER XII. 



Water, Heat, Air, and Light in the House 207 



Modern Conveniences. Water Supply. Plumbing. Hydrants 

 and Traps. Kindling a Fire; Matches. The Fireplace. Stoves. 

 Gas Stoves. Gasoline Stoves. Electric Stoves and Heaters. 

 Stream and Hot Water Heating. Thermostat. Exercises. -Need 

 of Ventilation. Methods of Ventilation. Ventilation without 

 Fans. Need of Moisture in Air. Light in the House. Glass. 

 Artificial Lighting. Gas for Lighting. Incandescent Mantles. 

 Gas Pipes and Fixtures. The Gas Meter. Acetylene for Lighting. 

 Electric Lighting. The Electric Meter. Summary. Exercises. 



