Page:Heroes of the telegraph (IA cu31924031222494).djvu/239

 itself further, without the aid of a telegraphist. Edison was running the cylinder which carried the embossed paper at a high speed one day, partly, as we are told, for amusement, and partly to test the rate at which a clerk could read a message. As the speed was raised, the paper gave out a humming rhythmic sound in passing under the stylus. The separate signals of the message could no longer be distinguished by the ear, and the instrument seemed to be speaking in a language of its own, resembling 'human talk heard indistinctly.' Immediately it flashed on the inventor that if he could emboss the waves of speech upon the paper the words would be returned to him. To conceive was to execute, and it was but the work of an hour to provide a vibrating diaphragm or tympanum fitted with an indenting stylus, and adapt it to the apparatus. Paraffined paper was selected to receive the indentations, and substituted for the Morse paper on the cylinder of the machine. On speaking to the tympanum, as the cylinder was revolved, a record of the vibrations was indented on the paper, and by re-passing this under the indenting point an imperfect reproduction of the sounds was heard. Edison 'saw at once that the problem of registering human speech, so that it could be repeated by mechanical means as often as might he desired, was solved.'

The experiment shows that it was partly by accident, and not by reasoning on theoretical knowledge, that the phonograph was discovered. The sound resembling 'human talk heard indistinctly' seems to have suggested it to his mind. This was the germ which fell upon the soil prepared for it. Edison's thoughts had been dwelling on the telephone;