The last of the ten sketches of Fig. 45 is taken from Edison’s first American Patent specification [No. 203,014, filed July 20, 1877], and shows a duplicated interrupter with springs and adjusting-screws combined with a tympanum. Further comment on this arrangement is needless, save to remark that in this patent for “_speaking_ telegraphs,” Edison himself describes the contact-apparatus which Reis termed an “interrupter,” as a “circuit-closer,” or in another place as “circuit-breaking connections,” and, in his British Patent quoted above, as a “tension-regulator.” It is evident that if Reis could transmit speech by an interrupter which closed and opened the circuit (always in proportion to the vibrations) there is no reason why Edison seventeen years afterwards should not accomplish the same result by a similar means. But it has lately been fashionable to deny that any such device as an interrupter mounted on springs can transmit speech at all! We have now compared with Reis’s transmitters several of the more modern inventions. It would be possible to carry comparison further were that course needed. We have not thought it worth while to rake up Edison’s now discarded lamp-black button transmitter; and we have not yet spoken of Crossley’s transmitter nor of Theiler’s transmitter, nor of their parent the Hughes’ microphone, nor of dozens of other forms. In some of these there is no specific “tympanum,” but only a sounding-board of pine-wood, and in most of them the points of loose-contact, where interruption more or less complete may occur, are multiplied. But they all come back in the end to Reis’s fundamental idea, namely that of setting the voice to vary the degree of contact in a mechanism which he called an interruptor, and which others have called a current-regulator (or, less correctly, a tension-regulator) which, because the degree of contact between its parts was varied, caused those parts to offer more or less resistance to the flow of the current, and thereby threw it into vibrations corresponding to those of the sound-wave impressed upon the tympanum. There is not a practical transmitter used in any of the telephone exchanges of Great Britain to-day that does not embody this principle.