CHAPTER XIV.

WIRELESS TELEGRAPHY.

Arrangements of Simple Circuits of Coil and Coherer for Receiving and Sending Messages. The Coherer. Carbon Coherer. Coherer without Filings. Aluminum Coherer. Steel Ball Coherer. The Oscillator. Clarke's Oscillator. Triple Oscillator. The Coil. Translating Devices. Air Conductor, etc. 248-265

INDEX 266

Bibliography 270

CONTENTS OF TABLES.

PAGE

GOOD PROPORTIONS OF CORE LENGTHS 7

TABLE OF "SECONDARY" WINDINGS 24

POLARITY TESTS 45

DIMENSIONS FOR DIFFERENT SPARK LENGTHS 50

TABLE SHOWING RESISTANCES AND FEET PER POUND OF COPPER AND GERMAN SILVER WIRE 64

SPECIFIC INDUCTIVE CAPACITY 119

WAVE LENGTHS AND TEMPERATURES 138-139

TABLE OF RELATIVE COSTS OF MATERIALS 191

LIST OF ILLUSTRATIONS.

FRONTISPIECE, THE QUEEN 45″ SPARK COIL.

FIG. PAGE

1. Section of Coil 4

2. Insulating Tube Ends 10

3. Sectional Winding 11

4. Section " First Method 12

5. " " Second Method 13

6. Proportional Diagram of Coil 15

7. Section Winder, End View 17

8. " " Face View 17

9. Assembly of Coils 18

10. Polechanging Switch 31

11. Disruptive Tesla Coil 35

12. Spark Coil for Gas Engine 38

13. Reproduction of a 32-inch Spark 47

14. Simple Medical Coil 53

15. Connections for Simple Medical Coil 55

16. Interchangeable Medical Coil 56

17. Vibrator for Medical Coil 60

18. Simple Contact Breaker 65

19. Imperfect Form of Contact Breaker 67

20. Superior Form of Contact Breaker 67

21. Spotteswoode Contact Breaker 69

22. Polechanging Contact Breaker 74

23. Wehnelt Interrupter 78

24. Ribbon Vibrator 81

25. Queen Contact Breaker 82

26. Adjustable Contact Breaker 86

27. Cone Contact Breaker 88

28. Coil Head Contact Breaker 89

29. Leyden Jar 101

30. Plate Condenser 102

31. Arrangement of Condenser Plates 104

32. Condenser Charging, First Method 110

33. " " Second Method 112

34. Adjustable Condenser 118

35. Spark between Balls 125

36. Short Spark between Balls 125

37. Sparkling Pane 125

38. Luminous Design 128

39. Electric Brush 128

40. Spectrum—Solar 132

41. Spectroscope and Coil 133

42. Simple Air Pump 141

43. Geissler Air Pump 144

44. Sprengel Air Pump 144

45. Solution Tube 150

46. Fluorescent Bulbs 150

47. Ruby Tube—Crookes 150

48. Iridio-platinum Tube—Crookes 151

49. Revolving Wheel 154

50. Tube Holder 157

51. Side View of Wheel 157

52. Geissler Tubes 160

53. Triangle on Disc 161

54. Maltese Cross on Disc 161

55. Gas Lighting Circuit 165

56. Connections for Gas Burners 169

57. Bartholdi Automatic Burner 172

58. Connections for Automatic Burner 174

59. The Grenet Cell 180

60. The Fuller Cell 184

61. The Gethins Cell 193

62. Lead Plate for Storage Cell 201

63. Wooden Separator 201

64. Charging with Rheostat 207

65. Charging with Lamps 207

66. Harrison Electrodes 211

67. Hydrometer 221

68. Hertz Resonator 227

69. Tesla Circuit 229

70. Tesla Cut Out 231

71. Tesla Cut Out, Top Plan 232

72. Circuit for X Ray Apparatus 237

73. Queen's Self-Regulating X Ray Tube 240

74. Transmitter for Wireless Telegraphy 250

75. Receiver for Wireless Telegraphy 252

76. The Branley Coherer 254

77. Clarke's Oscillator 259

78. Triple Oscillator 259

79. Air Wire Insulators 263