246 



Oersted, galvanic current on magnetic needle, 93. 

 Ohm, G. S., resistance unit, 74. 



Patents Caveat and application, 135. 



I M ante, storage- battery plates, (54. 



Pliny mentions electrical properties of amber, 67. 



loadstone, 20. 



Preece, double transmission, 114. 

 Prescott, Geo. B., quoted, 104, 106, 163, 174. 

 Ptolemy Philadelphus and loadstones, 20. 

 Pythagoras refers to natural magnets, 20. 



Radiophone, 171. 

 Railway train telegraphy, 131. 

 Richman, Prof., killed, 12. 

 Reiss, metallic telephone transmitters, 122. 

 Resistance, unit of, 74. 

 -coil, 118. 



Siemens, double transmission, 114. 



Selenium in radiophone, 172. 



Shephard, Charles S., induction-coil, 122. 



Stager, Gen. Anson, telegrapher, 110. 



Stearns, Joseph B., cures the " kick " in double 



transmission, 115. 

 Storage-battery, 24. 

 Slrada, loadstone telegraph, 88. 

 Submarine cables, Ch. XVII, 154. 



first lines, 154-5. 



Maury's deep-sea soundings, 155. 



first Atlantic, 156. 



retardations, 157. 



receiver, 158. 

 Sun-spots and magnetic storms, 37. 



Telautograph, Ch. XIX, 165. 

 Telegraph : 



heliostat, 68. 



