1898.] 



on Some Experiments with the Telephone 



becoming for a moment almost 

 invisible ; afterwards it assumes 

 a more smoky and luminous ap- 

 pearance, easily distinguishable 

 from the unexcited flame. 



When the sounds to be ob- 

 served come through the air, 

 they find access by a diaphragm 

 of tissue paper with which the 

 cavity is faced. This serves to 

 admit vibration while sufficiently 

 excluding air. To get the best 

 results the gas pressure must be 

 steady, and be carefully adjusted 

 to the maximum (about 1 inch) 

 at which the flame remains un- 

 disturbed. A hiss from the mouth 

 then brings about the transforma- 

 tion, while a clap of the hands or 

 the sudden crackling of a piece 

 of paper often causes extinction, 

 especially soon after the flame 

 has been lighted. 



When the vibrations to be 

 indicated are electrical, the tele- 

 phone takes the place of the disc 

 of tissue paper, and it is advan- 

 tageous to lead a short tube from 

 the aperture of the telephone into 

 closer proximity with the burner. 

 The earlier trials of the combina- 

 tion were comparative failures, 

 from a cause that could not at 

 first be traced. As applied, for 

 instance, to a Hughes' induction 

 balance, the apparatus failed to 

 indicate with certainty the in- 

 troduction of a shilling into one 

 of the cups, and the performance, 

 such as it was, seemed to dete- 

 riorate after a few minutes' ex- 

 perimenting. At this stage an 

 observation was made which ulti- 

 mately afforded a clue to the 

 anomalous behaviour. It was 

 found that the telephone became 

 dewed. At first it seemed incre- 

 dible that this could come from 



