it.
Subdivision of electric light. The filament. The glass bulb. Metallic
filaments. Vapor lamps. Directions for improvements. Heat in electric
lighting. Curious superstitions concerning electricity. Magnetism.
Amber. Discovery of the properties of a magnet. Electricity in
mountain regions. Early beliefs as to magnetism and electricity. The
lightning rod. Protests against using it. Pliny's explanation of
electricity.

XVII. POWER, AND VARIOUS OTHER ELECTRICAL MANIFESTATIONS Page 175

Early beliefs concerning the dynamo. Experiments with magnets.
Physical action of dynamo and motor. Electrical influence in windings.
Comparing motor and dynamo. How the current acts in a dynamo. Its
force in a motor. Loss in power transmission. The four ways in which
power is dissipated. Disadvantages of electric power. Its advantages.
Transmission of energy. High voltages. The transformer. Step-down
transformers. Electric furnaces. Welding by electricity. Merging the
particles of the joined ends.

XVIII. X-RAY, RADIUM AND THE LIKE Page 184

The camera and the eye. Actinic rays. Hertzian waves. High-tension
apparatus. Vacuum tubes. Character of the ultra-violet rays. How
distinguished. The infra-red rays. Their uses. X-rays not capable of
reflection. Not subject to refraction. Transmission through opaque
substances. Reducing rates of vibration. Radium. Radio-activity.
Radio-active materials. Pitchblende. A new form of energy. Electrical
source. Healing power. Problems for scientists.

LIST OF ILLUSTRATIONS

FIG.

1. Work bench Frontispiece

PAGE
2. Top of magnet-winding reel 14
3. Side of magnet-winding reel 14
4. Journal block 15
5. Plain magnet bar 19
6. Severed magnet 20
7. Reversed magnets 21
8. Horseshoe magnet 22
9. Earth's magnetic lines 23
10. Two permanent magnets 24
11. Magnets in earth's magnetic field 24
12. Armatures for magnets