Janniar, Joule, Laborde, Legat, Poggendorff, DuMoncel, Delezenne, Ferguson, Paul la Cour, Helmholtz, Gore, Sullivan and others, giving due credit to each. Then he described his undulating current and his electric-speaking telephone, for which letters-patent had been granted, and made it clear to his hearers that the essential factor in this problem was not the devising of a definite form of instrument or tube, nor an apparatus having definite structural peculiarities, nor the combining of a certain number of parts into an operating whole. It was to so cause the electric current to flow that the receiver would not only reproduce a few or a majority or about all of the spoken words that impinged on the diaphragm of the transmitter in the form of sound waves, but would reproduce each and all and every one of the variations in the articulations, loudness and pitch and quality, with all their varying characteristics, whether expressed in the slightest whisper, in the soft voice of the cultured woman, in the sonorous rounded sentences of the dignified professor, or in the quick, abrupt remarks of the man of affairs.
And it may be added that the discovery and practical application of the method so described by which the changes in the current strength in a telephone diaphragm were brought about forms the essential and underlying principle of every successful electric-speaking telephone designed since Alexander Graham Bell created the art of telephony, a composite art, combining magnetism, electricity, acoustics, phonetics, mechanics and engineering.
Gardiner Greene Hubbard was in charge of the Massachusetts educational exhibit at the Centennial Exposition. He insisted on placing the primitive telephones on exhibition in that section if no more suitable place could be secured. Alexander Graham Bell's time was too fully occupied with his professional work to give the subject any attention, and he really did not care whether the telephones were exhibited at the Centennial or not. Class examinations in his school were approaching, and he was far more interested in perfecting the knowledge of the members of his classes who were going forth to instruct deaf children in speech, and speech-reading, than in a mere display of an invention that he had completed, patented and had described in a public lecture. An exhibit meant more or less outlay. He was still in debt to his friends, and the funds to repay his friends must come from the income from his school. Therefore the school would be taken care of to the exclusion of the Centennial.
Nevertheless, Mr. Hubbard secured some telephones and certain telegraphic instruments, and placed them on a table in the space allotted to the department of education and science of Massachusetts, which occupied a portion of the gallery at the east end of the main building. This modest display was labeled 'Telegraphic and Telephonic Apparatus. By A. Graham Bell.' It included his system of harmonic telegraphy, and his method of transmitting articulate speech
