第68章

Mere knowledge, uncombined in the imagination, does not bear fruit in new inventions. It is from the union of different facts that a new idea springs. A scholar is apt to be content with the acquisition of knowledge, which remains passive in his mind. An inventor seizes upon fresh facts, and combines them with the old, which thereby become nascent. Through accident or premeditation he is able by uniting scattered thoughts to add a novel instrument to a domain of science with which he has little acquaintance. Nay, the lessons of experience and the scruples of intimate knowledge sometimes deter a master from attempting what the tyro, with the audacity of genius and the hardihood of ignorance, achieves. Theorists have been known to pronounce against a promising invention which has afterwards been carried to success, and it is not improbable that if Edison had been an authority in acoustics he would never have invented the phonograph. It happened in this wise.

During the spring of 1877, he was trying a device for making a telegraph message, received on one line, automatically repeat itself along another line. This he did by embossing the Morse signals on the travelling paper instead of merely inking them, and then causing the paper to pass under the point of a stylus, which, by rising and falling in the indentations, opened and closed a sending key included in the circuit of the second line. In this way the received message transmitted 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.' [T. A. Edison, NORTH AMERICAN REVIEW, June, 1888; New York ELECTRICAL REVIEW, 1888,]

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;he knew that a metal tympanum was capable of vibrating with all the delicacies of speech, and it occurred to him that if these vibrations could be impressed on a yielding material, as the Morse signals were embossed upon the paper, the indentations would reproduce the speech, just as the furrows of the paper reproduced the Morse signals. The tympanum vibrating in the curves of speech was instantly united in his imagination with the embossing stylus and the long and short indentations on the Morse paper; the idea of the phonograph flashed upon him. Many a one versed in acoustics would probably have been restrained by the practical difficulty of impressing the vibrations on a yielding material, and making them react upon the reproducing tympanum. But Edison, with that daring mastery over matter which is a characteristic of his mechanical genius, put it confidently to the test.

Soon after this experiment, a phonograph was constructed, in which a sheet of tinfoil was wrapped round a revolving barrel having a spiral groove cut in its surface to allow the point of the indenting stylus to sink into the yielding foil as it was thrust up and down by the vibrating tympanum. This apparatus-- the first phonograph--was published to the world in 1878, and created a universal sensation.

[SCIENTIFIC AMERICAN, March 30, 1878] It is now in the South Kensington Museum, to which it was presented by the inventor.