introduction. There he made the acquaintance of Professor Tyndall,

exhibited the telephone to the late King of England; and also won the friendship of the late King of the Belgians, with whom he took up the project of establishing telephonic communication between Belgium and England. At the time of his premature death he was engaged in installing the Edison quadruplex between Brussels and Paris, being one of the very few persons then in Europe familiar with the working of that invention. Meantime, the telephonic art in America was undergoing very rapid development. In March, 1878, addressing "the capitalists of the Electric Telephone Company" on the future of his invention, Bell outlined with prophetic foresight and remarkable clearness the coming of the modern telephone exchange. Comparing with gas and water distribution, he said: "In a similar manner, it is conceivable that cables of telephone wires could be laid underground or suspended overhead communicating by branch wires with private dwellings, country houses, shops, manufactories, etc., uniting them through the main cable with a central office, where the wire could be connected as desired, establishing direct communication between any two places in the city.... Not only so, but I believe, in the future, wires will unite the head offices of telephone companies in different cities; and a man in one part of the country may communicate by word of mouth with another in a distant place." All of which has come to pass. Professor Bell also suggested how this could be done by "the employ of a man in each central office for the purpose of connecting the wires as directed." He also indicated the two methods of telephonic tariff--a fixed rental and a toll; and mentioned the practice, now in use on long-distance lines, of a time charge. As a matter of fact, this "centralizing" was attempted in May, 1877, in Boston, with the circuits of the Holmes burglar-alarm system, four banking-houses being thus interconnected; while in January of 1878 the Bell telephone central-office system at New Haven, Connecticut, was opened for business, "the first fully equipped commercial telephone exchange ever established for public or general service." All through this formative period Bell had adhered to and introduced the magneto form of telephone, now used only as a receiver, and very poorly adapted for the vital function of a speech-transmitter. From August, 1877, the Western Union Telegraph Company worked along the other line, and in 1878, with its allied Gold & Stock Telegraph Company, it brought into existence the American Speaking Telephone Company to introduce the Edison apparatus, and to create telephone exchanges all over the country. In this warfare, the possession of a good battery transmitter counted very heavily in favor of the Western Union, for upon that the real expansion of the whole industry depended; but in a few months the Bell system had its battery transmitter, too, tending to equalize matters. Late in the same year patent litigation was begun which brought out clearly the merits of Bell, through his patent, as the original and first inventor of the electric speaking telephone; and the Western Union Telegraph Company made terms with its rival. A famous contract bearing date of November 10, 1879, showed that under the Edison and other controlling patents the Western Union Company had already set going some eighty-five exchanges, and was making large quantities of telephonic apparatus. In return for its voluntary retirement from the telephonic field, the Western Union Telegraph Company, under this contract, received a royalty of 20 per cent. of all the telephone earnings of the Bell system while the Bell patents ran; and thus came to enjoy an annual income of several hundred thousand dollars for some years, based chiefly on its modest investment in Edison's work. It was also paid several thousand dollars in cash for the Edison, Phelps, Gray, and other apparatus on hand. It secured further 40 per cent. of the stock of the local telephone systems of New York and Chicago; and last, but by no means least, it exacted from the Bell interests an agreement to stay out of the telegraph field. By March, 1881, there were in the United States only nine cities of more than ten thousand inhabitants, and only one of more than fifteen thousand, without a telephone exchange. The industry thrived under competition, and the absence of it now had a decided effect in checking growth; for when the Bell patent expired in 1893, the total of telephone sets in operation in the United States was only 291,253. To quote from an official Bell statement: "The brief but vigorous Western Union competition was a kind of blessing in disguise. The very fact that two distinct interests were actively engaged in the work of organizing and establishing competing telephone exchanges all over the country, greatly facilitated the spread of the idea and the growth of the business, and familiarized the people with the use of the telephone as a business agency; while the keenness of the competition, extending to the agents and employees of both companies, brought about a swift but quite unforeseen and unlooked-for expansion in the individual exchanges of the larger cities, and a corresponding advance in their importance, value, and usefulness." The truth of this was immediately shown in 1894, after the Bell patents had expired, by the tremendous outburst of new competitive activity, in "independent" country systems and toll lines through sparsely settled districts--work for which the Edison apparatus and methods were peculiarly adapted, yet against which the influence of the Edison patent was invoked. The data secured by the United States Census Office in 1902 showed that the whole industry had made gigantic leaps in eight years, and had 2,371,044 telephone stations in service, of which 1,053,866 were wholly or nominally independent of the Bell. By 1907 an even more notable increase was shown, and the Census figures for that year included no fewer than 6,118,578 stations, of which 1,986,575 were "independent." These six million instruments every single set employing the principle of the carbon transmitter--were grouped into 15,527 public exchanges, in the very manner predicted by Bell thirty years before, and they gave service in the shape of over eleven billions of talks. The outstanding capitalized value of the plant was $814,616,004, the income for the year was nearly $185,000,000, and the people employed were 140,000. If Edison had done nothing else, his share in the creation of such an industry would have entitled him to a high place among inventors. This chapter is of necessity brief in its reference to many extremely interesting points and details; and to some readers it may seem incomplete in its references to the work of other men than Edison, whose influence on telephony as an art has also been considerable. In reply to this pertinent criticism, it may be pointed out that this is a life of Edison, and not of any one else; and that even the discussion of his achievements alone in these various fields requires more space than the authors have at their disposal. The attempt has been made, however, to indicate the course of events and deal fairly with the facts. The controversy that once waged with great excitement over the invention of the microphone, but has long since died away, is suggestive of the difficulties involved in trying to do justice to everybody. A standard history describes the microphone thus: "A form of apparatus produced during the early days of the telephone by Professor Hughes, of England, for the purpose of rendering faint, indistinct sounds distinctly audible, depended for its operation on the changes that result in the resistance of loose contacts. This apparatus was called the microphone, and was in reality but one of the many forms that it is possible to give to the telephone transmitter. For example, the Edison granular transmitter was a variety of microphone, as was also Edison's transmitter, in which the solid button of carbon was employed. Indeed, even the platinum point, which in the early form of the Reis transmitter pressed against the platinum contact cemented to the centre of the diaphragm, was a microphone." At a time when most people were amazed at the idea of hearing, with the aid of a "microphone," a fly walk at a distance of many miles, the priority of invention of such a device was hotly disputed. Yet without desiring to take anything from the credit of the brilliant American, Hughes, whose telegraphic apparatus is still in use all over Europe, it may be pointed out that this passage gives Edison the attribution of at least two original forms of which those suggested by Hughes were mere variations and modifications. With regard to this matter, Mr. Edison himself remarks: "After I sent one of my men over to London especially, to show Preece the carbon transmitter, and where Hughes first saw it, and heard it--then within a month he came out with the microphone, without any acknowledgment whatever. Published dates will show that Hughes came along after me." There have been other ways also in which Edison has utilized the peculiar property that carbon possesses of altering its resistance to the passage of current, according to the pressure to which it is subjected, whether at the surface, or through closer union of the mass. A loose road with a few inches of dust or pebbles on it offers appreciable resistance to the wheels of vehicles travelling over it; but if the surface is kept hard and smooth the effect is quite different. In the same way carbon, whether solid or in the shape of finely divided powder, offers a high resistance to the passage of electricity; but if the carbon is squeezed together the conditions change, with less resistance to electricity in the circuit. For his quadruplex system, Mr. Edison utilized this fact in the construction of a rheostat or resistance box. It consists of a series of silk disks saturated with a sizing of plumbago and well dried. The disks are compressed by means of an adjustable screw; and in this manner the resistance of a circuit can be varied over a wide range. In like manner Edison developed a "pressure" or carbon relay, adapted to the transference of signals of variable strength from one circuit to another. An ordinary relay consists of an electromagnet inserted in the main line for telegraphing, which brings a local battery and sounder circuit into play, reproducing in the local circuit the signals sent over the main line. The relay is adjusted to the weaker currents likely to be received, but the signals reproduced on the sounder by the agency of the relay are, of course, all of equal strength, as they depend upon the local battery, which has only this steady work to perform. In cases where it is desirable to reproduce the signals in the local circuit with the same variations in strength as they are received by the relay, the Edison carbon pressure relay does the work. The poles of the electromagnet in the local circuit are hollowed out and filled up with carbon disks or powdered plumbago. The armature and the carbon-tipped poles of the electromagnet form part of the local circuit; and if the relay is actuated by a weak current the armature will be attracted but feebly. The carbon being only slightly compressed will offer considerable resistance to the flow of current from the local battery, and therefore the signal on the local sounder will be weak. If, on the contrary, the incoming current on the main line be strong, the armature will be strongly attracted, the carbon will be sharply compressed, the resistance in the local circuit will be proportionately lowered, and the signal heard on the local sounder will be a loud one. Thus it will be seen, by another clever juggle with the willing agent, carbon, for which he has found so many duties, Edison is able to transfer or transmit exactly, to the local circuit, the main-line current in all its minutest variations. In his researches to determine the nature of the motograph phenomena, and to open up other sources of electrical current generation, Edison has worked out a very ingenious and somewhat perplexing piece of apparatus known as the "chalk battery." It consists of a series of chalk cylinders mounted on a shaft revolved by hand. Resting against each of these cylinders is a palladium-faced spring, and similar springs make contact with the shaft between each cylinder. By connecting all these springs in circuit with a galvanometer and revolving the shaft rapidly, a notable deflection is obtained of the galvanometer needle, indicating the production of electrical energy. The reason for this does not appear to have been determined. Last but not least, in this beautiful and ingenious series, comes the "tasimeter," an instrument of most delicate sensibility in the presence of heat. The name is derived from the Greek, the use of the apparatus being primarily to measure extremely minute differences of pressure. A strip of hard rubber with pointed ends rests perpendicularly on a platinum plate, beneath which is a carbon button, under which again lies another platinum plate. The two plates and the carbon button form part of an electric circuit containing a battery and a galvanometer. The hard-rubber strip is exceedingly sensitive to heat. The slightest degree of heat imparted to it causes it to expand invisibly, thus increasing the pressure contact on the carbon button and producing a variation in the resistance of the circuit, registered immediately by the little swinging needle of the galvanometer. The instrument is so sensitive that with a delicate galvanometer it will show the impingement of the heat from a person's hand thirty feet away. The suggestion to employ such an apparatus in astronomical observations occurs at once, and it may be noted that in one instance the heat of rays of light from the remote star Arcturus gave results.