Material, non-conducting, 90. Maximum, 154. Measure, 55, 56, 60, 62. Measurement, 62. Measuring devices, 27. Measuring instruments, 8. Mechanism, 47, 180. Medical batteries, 99. Mercury, 63, 169. Metal base, 73. Mica, 186. Microphone, 118, 119, 120. Millimeter, 63. Minus, 34. Minus sign, 21. Morse code, 76. Motor, 7, 21, 27, 46, 47, 62, 82, 99, 150, 176, 180. Mouthpiece, 115. Mouthpiece rays, 188. Moving field, 117. Multiple, 168. Musical scale, 111. N Negative, 21, 35, 36, 68, 83, 86, 87, 94, 125, 151, 152, 154, 165, 177, 178, 179. Neutral, 125. Neutral plate, 84. Nickel, 136. Nickel plating, 132. Nitrate of silver, 62. Nitrogen, 126. Non-conducting material, 90. Non-conductor, 164. Non-magnetic, 19. North pole, 20, 21, 22, 23, 25, 50, 54, 156. Number plate, 75. N-ray, 188. O Ohms, 60, 63. Ohms, international, 63. Ohms law, 7. Operator, 95, 118. Oscillating, 99, 105. Osmium, 169. Oxides, 125. Oxidizing, 183. Oxygen, 35, 123, 125, 126, 128, 129, 169. P Packing ring, 124. Paraffine, 56, 100, 101, 102. Paraffine wax, 86. Parallel, 87, 88, 89. Parallel switch bar, 67. Parallel wires, 28, 49. Partition, 124. Peon, 13. Percolate, 128. Periodicity, 159. Periods of alternations, 149. Permanent, 18, 19, 50. Permanent magnet, 25, 38, 46, 50, 172. Phase, 19. Phenomenon, 27, 65. Photograph, 186. Physical, 21. Pile, voltaic, 33. Pipe, 61. Pitchblende, 186. Pivot pin, 53. Pivotal, 22. Plane, 13. Plate, 57, 93. Plate, contact, 67, 68, 79. Plate, copper, 33, 35, 58, 67. Plate, negative, 84. Plate, number, 75. Plate, positive, 84, 88. Plate, zinc, 33. Platinum, 13, 57, 137. Pliers, 14. Plus sign, 21, 24. Pointer, 53. Polarity, 154, 177, 178, 179. Polarization, 35. Pole, north, 20, 21, 22, 23, 25, 50, 54, 156. Pole piece, 40, 42. Pole, south, 20, 21, 22, 25, 50, 54, 156. Poles, 177, 179. Polonium, 186. Porcelain, 86. Porous, 85. Positive, 4, 21, 25, 36, 40, 68, 83, 86, 87, 94, 123, 125, 151, 152, 153, 155, 165. Post, binding, 52, 71. Potentiality, 105, 109. Power, 38, 186. Power, candle, 89, 139. Precipitate of lead, 83, 85. Precision, 7. Pressure, 87. Primary, 35, 62, 98, 134, 142, 159, 184. Primary battery, 7, 99. Primary circuit, 99. Primary coil, 106, 109. Prime conductor, 6. Projected, 185. Propagated, 105, 185. Properties, 55. Purification, 123, 128. Purifier, 126, 131. Push button, 65, 68, 69, 70, 76, 79. Q Quantity, 55, 60, 61, 138. Quartz, 186. R Radio-activity, 186. Radium, 184, 185, 187, 188. Ratchet drill, 13. Reaction, 148. Receiver, 12, 90, 97, 121, 122. Receiving station, 109. Rectangular, 69. Rectifiers, 146. Red lead, 83, 84. Reel, 13. Reflected, 185. Refraction, 185. Refractory, 182. Register, 57. Removable, 54. Removable cap, 73. Repel, 20. Repulsion, 21, 128. Reservoir, 61, 62. Resiliency, 99. Resistance, 7, 36, 37, 60, 63, 99, 135, 136, 137, 138, 140, 141, 156, 157, 163, 166, 168.