All About Inventions and Discoveries
The Romance of modern scientific and mechanical Achievements

148 All About Inventions set into vibration over the pole of its electro-magnet by Watson’s snapping had generated an electric current which fulfilled fully Bell’s dream of being able to talk by telegraph if once a means could be discovered of causing a current of electricity to vary in its intensity in precisely the same way as the air waves vary in density during the production of a sound. As Bell explained his theory, Watson listened in amazement, which became accentuated when Bell advanced the opinion that if an instrument could transmit one sound so perfectly it should be possible, by introducing modifications, to transmit any sound, and even the human voice! The excitement of Bell and the sensation of being upon the verge of a great discovery drove all the tired feeling out of Watson. The two men spent the whole afternoon twanging springs and trying various combinations as they occurred to them. While Bell was experimenting he was thinking hard. Before they finished work, long after the sun had set, Bell had prepared a rough idea of his conception for a talking-wire or telephone, which he urged Watson to make as soon as he could. He directed Watson to take one of the harmonic receivers and to attach it to a drumhead, expressing the firm conviction that when he talked against the drumhead, the spring attached to it would be compelled to follow the vocal vibration and transmit articulate speech instead of merely its own monotone twang. Watson by now had become so infected with Bell’s excited enthusiasm that he commenced the con- struction of the instrument roughly outlined by Bell directly the twain parted that afternoon. By toil-