Ducretet’s system 192 Ducretet’s speaker 193 Boudet’s speaker 195 Gaiffe’s thermoscope 197 Blyth’s system 199 Microphone as a speaking instrument 200 Hughes’s system 203 Other arrangements of microphones 205 Varcy’s and Trouvé’s microphones 207 Lippens’s microphone 209 Hughes’s experiments 211 Hughes’s theory 215 Microphone used as thermoscope 217 Edison’s thermoscope 219 Experiments in London 220 Experiment at Bellinzona 223 _APPLICATIONS OF MICROPHONE._ Its application to scientific research 226 Application to telephonic relays 229 Application to surgery 232 Various applications 236 _EXTERNAL INFLUENCE ON TELEPHONIC TRANSMISSIONS._ Disturbing influences 239 Confusion of circuits 241 Induced reactions 243 Mr. Preece’s suggestions 245 Effects of heat and moisture 249 _ESTABLISHMENT OF TELEPHONE STATION._ Pollard and Garnier’s system 252 Bréguet and Roosevelt’s system 254 Edison’s system 257 _CALL-BELLS AND ALARUMS._ Weinhold’s system 262 Dutertre and Gouault’s system 264 Puluj’s system 266 Chiddey’s system 267 _APPLICATIONS OF TELEPHONE._ Its application to simultaneous transmissions 270 Bell’s system 273 Lacour’s system 276 Gray’s system 282 _VARIOUS USES OF THE TELEPHONE._