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 25 13. Magnetized field 26 14. Magnetized bar 26 15. Direction of current 27 16. Direction of induction current 28 17. Frictional-electricity machine 30 18. Leyden jar 32 19. Galvanic electricity. Crown of cups 33 20. Voltaic electricity 34 21. Primary battery 36 22. Dynamo field and pole piece 39 23. Base and fields assembled 41 24. Details of the armature, core 42 25. Details of the armature, body 42 26. Armature Journals 43 27. Commutator 43 28. End view of armature, mounted 44 29. Top view of armature on base 45 30. Field winding 47 31. Series-wound 47 32. Shunt-wound 48 33. Compound-wound 48 34. Compass magnet, swing to the right 50 35.