suit Adler, Max, (Kausalinit und Teleologie im Streite und die Wissenschaft) (in Marx Studien, Vol. I, Vienna 1904); Bosanquet, (Meaning of Teleology> (in (Proceedings> of the British Academy, London 1906); Erhardt, Franz, (Mechanismus unde Teleologic." (Leip zig 1890) Janet, Paul, (Final Causes> (Eng: trans. by W. Affieck, New York 1883) ; band, (History of Philosophy> ; HOffding, (His tory of Modern Philosophy' • Spinoza,
uate School, Cornell University. ' would do the same for any sound, even that speech, this experiment revealed to him the poi sibility of accomplishing the desired results. The next day he gave instructions for the making of his first real telephone, known as the °Gallows° type. (Fig. 4). It consisted of a framework carrying an electromagnet with its reed armature, the free end of which was attached to the centre of a small drumhead of gold-beater's skin. A mouthpiece was provided diaphragm. With these instruments, Professor Bell speaking, and Mr. Watson listening, the first complete articulate telephone message was transmitted.
On 9 Oct. 1876 the first reciprocal conversa tion took place over an outdoor line, two miles long, between Boston and Cambridgeport, Mass. The instruments (Fig. 7) had, as diaphragms, thin iron discs which responded to the voice vibrations. Close to, but not touching, the cen tre of the diaphragm was the core of an electro magnet, the windings of which were connected in series with a battery, the line and a similar instrument at the other end. With these instru ments was carried on a sustained conversation which was fully reported in the next morning's papers as the latest startling scientific achieve ment.
for speaking purposes. With this instrument, speech sounds were transmitted over a short line and heard by means of a second instrument of like character. From this time on, many forms of receivers and transmitters were ex perimented with until, on 10 March 1876, the first articulate complete sentences were trans mitted. Professor Bell was then experimenting with his liquid transmitter. (Fig. 5). This instrument consisted essentially of a diaphragm, capable of being vibrated by the voice, to the centre of which was attached a small conduct Professor Bell exhibited his telephone inven tions at the Centennial Exposition in Philadel phia in 1876. There he demonstrated, before the judges of the exposition and a large number ing rod dipping into acidulated water con tained within a small cup' A large flaring mouthpiece was provided and the whole was suitably mounted on a frame and base with connecting terminals. This transmitter was
connected in series with a battery and a tuned harmonic receiver. (Fig. 6). Undulating current was produced by the change in re sistance of the circuit as more or less of the rod was immersed due to the vibration of the of people, his liquid transmitter (Fig. 5) ; iron box receiver (Fig. 8) ; single pole membrane telephone (Fig. 9), and other types of instru ments. As a result of this exhibition of the telephone its fame spread rapidly.
Work of Early Investigators Preceding Bell.— The idea of applying electricity for the transmission of sound arose as soon as the effects of electric telegraphy were observed. Page, in 1837, discovered that a magnetic bar could emit sounds when rapidly magnetized and demagnetized. Electric vibrators devised by Macaulay, Wagner and Neef and adapted to produce musical sounds by Froment and Petrina in 1847 to 1852, showed that the transmission of sound to a distance was not impossible. Bourseul, in 1854, suggested that if one spoke near a movable disc sufficiently flexible to lose none of the vibrations of the voice, this disc, by alternately making and breaking the current from a battery, might cause another disc, at a distance, to execute the same vibrations simul taneously. Reis, in 1870, invented a musical telephone that, by alternately making and break ing an electric circuit, could transmit musical tones over a wire to a distant point. Reis' work, although urged as an anticipation of Bell, never found favor in the courts during the ex tensive patent litigation that followed Bell's invention because his scheme was based on mak ing and breaking a current, which cannot trans mit speech. The United States Supreme Court said .eto follow Reis is to fail, but to follow Bell is to succeeds The publication of Profes sor Bell's invention brought forth many claim ants to priority. After years of litigation in which the state of the art and the claims of others were considered exhaustively, priority for the invention of the telephone was finally awarded to Professor Bell. While Professor Bell, by means of lectures on the telephone, was arousing public interest in his invention, devel opment work was begun to make the instru ments more practical for general use. The box type (Figs. 10 and 11), which was the best form thus far devised, was not adapted to be held in the hand. The inconvenience of the box telephone led to the development of a style of instrument which could be held in the hand readily and used for transmitting or receiving as desired.