Chapter VI.--THE ELECTRIC TELEGRAPH.

1. Chapter 1 2. Chapter I.--THE STEAM-ENGINE. 3. Chapter II.--THE CONVERSION OF HEAT ENERGY 4. Chapter III.--THE STEAM TURBINE. 5. Chapter IV.--THE INTERNAL-COMBUSTION ENGINE. 6. Chapter V.--ELECTRICAL APPARATUS. 7. Chapter VI.--THE ELECTRIC TELEGRAPH. 8. Chapter VII.--WIRELESS TELEGRAPHY. 9. Chapter VIII.--THE TELEPHONE. 10. Chapter IX.--DYNAMOS AND ELECTRIC MOTORS. 11. Chapter X.--RAILWAY BRAKES. 12. Chapter XI.--RAILWAY SIGNALLING. 13. Chapter XII.--OPTICS. 14. Chapter XIII.--THE MICROSCOPE, THE TELESCOPE, 15. Chapter XIV.--SOUND AND MUSICAL INSTRUMENTS. 16. Chapter XV.--WIND INSTRUMENTS. 17. Chapter XVI.--TALKING-MACHINES. 18. Chapter XVII.--WHY THE WIND BLOWS. 19. Chapter XVIII.--HYDRAULIC MACHINERY. 20. Chapter XIX.--HEATING AND LIGHTING. 21. Chapter XX.--VARIOUS MECHANISMS. 22. Chapter I. 23. Chapter II. 24. Chapter III. 25. Chapter IV. 26. Chapter V. 27. Chapter VI. 28. Chapter VII. 29. Chapter VIII. 30. Chapter IX. 31. Chapter X. 32. Chapter XI. 33. Chapter XII. 34. 112. A _compound_ lens is needed, made up of a _crown_ glass convex 35. Chapter XIII. 36. 131. Two rays, A _b_, A _c_, from a point A strike the mirror M at the 37. Chapter XIV. 38. Chapter XV. 39. 138. (2.) _Reed_ pipes--that is, pipes used in combination with a 40. Chapter XVI. 41. Chapter XVII. 42. Chapter XVIII. 43. 176. The piston now is solid, and the upper valve is situated in the 44. Chapter XIX. 45. Chapter XX.