so vary the strength of current as to reproduce sonorous vibrations; but there is no record of this experiment having been tried. Edison proposed to utilise the fact that the resistance of carbon varied under pressure. He had independently discovered this peculiarity of carbon, but it had been previously described by Du Moncel. ... The first carbon transmitter was constructed in 1878 by Edison." _W. H. Preece, and J. Maier, The Telephone, chapter 3-4._ In a pamphlet distributed at the Columbian Exposition, Chicago, 1893, entitled "Exhibit of the American Bell Telephone Co.," the following statements are made: "At the Centennial Exposition, in Philadelphia, in 1876, was given the first general public exhibition of the telephone by its inventor, Alexander Graham Bell. To-day, seventeen years later, more than half a million instruments are in daily use in the United States alone, six hundred million talks by telephone are held every year, and the human voice is carried over a distance of twelve hundred miles without loss of sound or syllable. The first use of the telephone for business purposes was over a single wire connecting only two telephones. At once the need of general inter-communication made itself felt. In the cities and larger towns exchanges were established and all the subscribers to any one exchange were enabled to talk to one another through a central office. Means were then devised to connect two or more exchanges by trunk lines, thus affording means of communication between all the subscribers of all the exchanges so connected. This work has been pushed forward until now have been gathered into what may be termed one great exchange all the important cities from Augusta on the east to Milwaukee on the west, and from Burlington and Buffalo on the north to Washington on the south, bringing more than one half the people of this country and a much larger proportion of the business interests, within talking distance of one another. ... The lines which connect Chicago with Boston, via New York, are of copper wire of extra size. It is about one sixth of an inch in diameter, and weighs 435 pounds to the mile. Hence each circuit contains 1,044,000 pounds of copper. ... In the United States there are over a quarter of a million exchange subscribers, and ... these make use of the telephone to carry on 600,000,000 conversations annually. There is hardly a city or town of 5,000 inhabitants that has not its Telephone Exchange, and these are so knit together by connecting lines that intercommunication is constant." The number of telephones in use in the United States, on the 20th of December in each year since the first introduction, is given as follows; 1877, 5,187; 1878, 17,567; 1879, 52,517; 1880, 123,380; 1881, 180,592; 1882, 237,728; 1883, 298,580;