“At the first condensation (of air vibrations) the hammer-shaped little wire _d_ (G in our illustration), will be pushed back. At the succeeding rarefaction it cannot follow the return vibration of the membrane, and the current going through the little strip (of platinum) remains interrupted so long as until the membrane driven by a new condensation presses the little strip against _d_ (the hammer G) once more. In this way each sound wave effects an opening and closing of the current.” [Illustration: FIG. 56.--PROF. BELL’S TELEPHONE, MARCH 7, 1876.] Reis evidently did not know how to make the vibrations of his diaphragm translate themselves into exactly commensurate and correlated electric impulses of equal rapidity, range, and quality. If he had done this, he would have had a speaking telephone, but a make-and-break contact could never do it, and hence he in his later instruments attached to them a telegraphic key in order that the sending operator might communicate with the receiving operator. If Reis’ telephone had been a speaking telephone, this would have been unnecessary. Furthermore, it is inconceivable how the intelligent, progressive, and scientific Germans could have failed to have given to a speaking telephone in 1860 the immediate honor and attention that it deserved. In America, the Bell speaking telephone, invented in 1876, was known all over the civilized world the same year. Reis’ broken contact circuit would transmit musical tones, because musical tones vary chiefly in rapidity of vibration, rather than in range, or quality, and the chattering contacts of Reis’ telephone would transmit musical tones because said contracts could be adjusted to the practically uniform range of vibration. Prof. Bell, however, had made a special study of articulate speech, and knew that speech was not essentially musical, but was composed of an irregular and discordant medley of vowel and consonant sounds, whose vibrations varied not only in pitch or rapidity like musical tones, but also in the quality or kind of vibrations as to range and loudness. In his invention, therefore, he did not make and break the circuit as did Reis, through the contact points, but he used the more sensitive plan of a constantly closed circuit, and merely caused the current to undulate in it by a principle of magnetic induction. This principle was first discovered by Oersted, and developed into the well known fact that when a piece of iron is moved back and forth from the poles of an electro-magnet an induced current is made to oscillate in the helix of the electro-magnet. The difference between Reis’ separating make-and-break circuit, and the Bell continuous but undulating current, might be illustrated by the difference between the impulses delivered by the beating of the drum sticks on the head of a drum, on the one hand, and the alternate pulling and slackening of a kite cord, on the other. In the successive impacts on the head of a drum there could not be so