x ELEMENTS OF GENERAL SCIENCE 



PAGE 



and its uses. How to make a common kind of electric circuit. 

 Another kind of circuit. Series and parallel connections. Unite 

 used in measuring electricity. Practical uses of voltmeters and 

 ammeters. How to read the watt-hour meter Uses of electric 

 heatino- devices. Electric advertising signs. Other devices uti- 

 lizing heating effects. The motion-picture machine. 



CHAPTER XVIII. CHEMICAL EFFECTS OF ELECTRIC 

 CURRENTS 



Questions for Discussion. How to plate articles with copper. The 

 rate of deposit. The lead storage cell and some of its uses. The 

 automobile storage battery. 



CHAPTER XIX. THE MAGNETIC EFFECTS OF ELECTRIC 



CURRENTS . . 224 



Questions for Discussion. Permanent magnets and their uses. The 

 region about a magnet. How a magnet is produced by an electric 

 current. Magnetism in a coil of wire carrying a current. Uses of 

 small electromagnets. Uses of large electromagnets. The simple 

 electric motor. Danger of electrical injuries. The essential parts 

 of a motor. Different kinds of motors. Domestic and commercial 

 uses of motors. Electric bells in a modern city residence. Uses 

 of the transformer. The supplying of energy to the home. Use of 

 direct and alternating currents. Electrical industries. 



PART IV. THE EARTH IN RELATION TO OTHER 

 ASTRONOMICAL BODIES 



CHAPTER XX. THE MOON, PLANETS, AND COMETS .... 243 



Questions for Discussion. Introductory statement. Phases of the 

 moon. Amount of light from the moon. Distance and size of the 

 moon. Atmosphere and water on the moon. Erosion and craters. 

 Climate of the moon. Eclipses. Planets which revolve about the 

 sun. Mercury and Venus. The red planet Mars. The "canals" 

 upon Mars. Jupiter. Saturn. The discovery of Uranus. The 

 discovery of Neptune. Comets. Visible comets. 



CHAPTER XXI. THE SUN AND OTHER STARS 264 



Questions for Discussion. Distance and size of the sun. The 

 earth's orbit and the size of the sun. Source of the sun's heat. 

 Storms on the sun. Constitution of the sun. Nature and distance 

 of the stars. Stars of different magnitude. The constellations. 

 Stars visible in October, November, and December. Stars visible 

 in January, February, and March. Stars visible in April, May, 

 and June. Stars visible in July, August, and September. The 

 Milky Way, or Galaxy. 



