第69章

The phonograph was first publicly exhibited in England at a meeting of the Society of Telegraph Engineers, where its performances filled the audience with astonishment and delight. A greeting from Edison to his electrical brethren across the Atlantic had been impressed on the tinfoil, and was spoken by the machine. Needless to say, the voice of the inventor, however imperfectly reproduced, was hailed with great enthusiasm, which those who witnessed will long remember. In this machine, the barrel was fitted with a crank, and rotated by handle. Aheavy flywheel was attached to give it uniformity of motion. A sheet of tinfoil formed the record, and the delivery could he heard by a roomful of people. But articulation was sacrificed at the expense of loudness. It was as though a parrot or a punchinello spoke, and sentences which were unexpected could not be understood. Clearly, if the phonograph were to become a practical instrument, it required to be much improved. Nevertheless this apparatus sufficiently demonstrated the feasibility of storing up and reproducing speech, music, and other sounds. Numbers of them were made, and exhibited to admiring audiences, by license, and never failed to elicit both amusement and applause. To show how striking were its effects, and how surprising, even to scientific men, it may be mentioned that a certain learned SAVANT, on hearing it at a SEANCE of the Academie des Sciences, Paris, protested that it was a fraud, a piece of trickery or ventriloquism, and would not be convinced.

After 1878 Edison became too much engaged with the development of the electric light to give much attention to the phonograph, which, however, was not entirely overlooked. His laboratory at Menlo Park, New Jersey, where the original experiments were made, was turned into a factory for making electric light machinery, and Edison removed to New York until his new laboratory at Orange, New Jersey, was completed. Of late he has occupied the latter premises, and improved the phonograph so far that it is now a serviceable instrument. In one of his 1878 patents, the use of wax to take the records in place of tinfoil is indicated, and it is chiefly to the adoption of this material that the success of the 'perfected phonograph' is due. Wax is also employed in the 'graphophone' of Mr. Tainter and Professor Bell, which is merely a phonograph under another name. Numerous experiments have been made by Edison to find the bees-wax which is best adapted to receive the record, and he has recently discovered a new material or mixture which is stated to yield better results than white wax.

The wax is moulded into the form of a tube or hollow cylinder, usually 41/4 inches long by 2 inches in diameter, and 1/8 inch thick. Such a size is capable of taking a thousand words on its surface along a delicate spiral trace; and by paring off one record after another can be used fifteen times. There are a hundred or more lines of the trace in the width of an inch, and they are hardly visible to the naked eye.

Only with a magnifying glass can the undulations caused by the vibrating stylus be distinguished. This tube of wax is filed upon a metal barrel like a sleeve, and the barrel, which forms part of a horizontal spindle, is rotated by means of a silent electro-motor, controlled by a very sensitive governor. A motion of translation is also given to the barrel as it revolves, so that the marking stylus held over it describes a spiral path upon its surface. In front of the wax two small metal tympanums are supported, each carrying a fine needle point or stylus on its under centre. One of these is the recording diaphragm, which prints the sounds in the first place; the other is the reproducing diaphragm, which emits the sounds recorded on the wax. They are used, one at a time, as the machine is required, to take down or to render back a phonographic message.

The recording tympanum, which is about the size of a crown-piece, is fitted with a mouthpiece, and when it is desired to record a sentence the spindle is started, and you speak into the mouthpiece. The tympanum vibrates under your voice, and the stylus, partaking of its motion, digs into the yielding surface of the wax which moves beneath, and leaves a tiny furrow to mark its passage. This is the sonorous record which, on being passed under the stylus of the reproducing tympanum, will cause it to give out a faithful copy of the original speech. A flexible india-rubber tube, branching into two ear-pieces, conveys the sound emitted by the reproducing diaphragm to the ears. This trumpet is used for privacy and loudness; but it may be replaced by a conical funnel inserted by its small end over the diaphragm, which thereby utters its message aloud.