construction of the speaking telephone of to-day. When used in connection with his articulating transmitter, which was developed at a later date, articulate words have been received upon it; and when a duplicate of the instrument is inserted in a closed circuit, which includes a galvanic battery, it becomes a speaking telephone capable of acting both as a transmitter and as a receiver. Mr. Gray did not know at that time, however, that he could use it as a transmitter, although he had fully demonstrated its ability to receive sounds of varying quality. At that date his conception of a transmitter for the transmission of articulate words was a mechanism which would employ such tones as were needed, and would enable one to manipulate them in whatever manner was requisite to produce the desired effect. In other words, he supposed it would be necessary to construct a mechanism similar to the vocal organs of the throat, which would mold electrical waves into the same form that the air is molded when a spoken word is uttered. This seemed too complicated a machine to be easily constructed; hence he determined to experiment particularly in the direction of the more perfect transmission of composite tones, so that each individual tone would have its individuality and place properly preserved in the clang of which it was a part; and to the analysis of the same at the receiving end, so that any particular tone would respond upon one instrument, and one only. This general result once attained, it was his purpose to make an application of it to multiple, printing, and autographic telegraphy. While engaged in these experiments he was continually on the alert for developments that might assist him to solve the interesting problem already before his mind, that of transmitting spoken words. Shortly after he constructed a transmitter, consisting of a revolving shaft, upon which were mounted two eccentric cams, having one or more projections. These actuated two small levers, causing them to vibrate upon their respective break-points, through which points a battery current passed. He employed, in connection with this transmitter, a receiver which was adapted to the reception of all varieties of sounds.
When this apparatus was put in operation a sound of peculiar quality, not unlike that of the human voice when in great distress, proceeded from the receiver. By altering the tension of the spring in various ways he was able to imitate many different sounds involving the vowels only, and succeeded, among other things, in producing a groan with all its inflections in the greatest perfection. Up to the time of making this experiment Mr. Gray had associated in his mind, in connection with transmission of spoken words, a complicated mechanism. This experiment produced an entire change in his views, and he came to the conclusion that in solving the problem of transmitting spoken words it was not necessary to consider the mechanism of the vocal organs at all, but simply the physical results produced in the atmosphere by them, and all that was necessary, therefore, was to devise a transmitter that would
