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ture to the foregoing, when the vacuum tube is employed as a wireless tele- phone. Hundreds of the bulbs are con- nected to a powerful battery or dyna- mo. The voice spoken into a telephone transmitter connected in the circuit so disturbs the electrical balance of the bulbs that powerful waves are created. The most striking example of this ap- plication was the recent feat of tele- phoning wirelessly from Washington to Hawaii.

Another use of the audion is in re- laying the current that carries the

��Popular Sciejire Monthly

By the combination of some of the foregoing properties of the vacuum bulb, the uncanny but delightful result, electrical music, is attained. The idea of converting the silently flowing elec- tric current into strains of the most bewitching music is not entirely new. Many readers will recall the telhar-- monium, which was built at great cost several years ago and with which elec- trical concerts in the home were prophe- sied. But the telharmonium required dynamos of such variety and size that it was eventually given up because of

���In appearance the audion closely resembles an ordinary electric lamp bulb. Euilt into

the bulb close to the filament are two metal electrodes which are connected in such a

way that a perfect electrical balance is maintained between them. When the wireless

wave disturbs this balance, the disturbance is heard in the telephone receivers

��voice over long distance telephone lines.

The other applications of the audion are of a laboratory nature. One of these applications is transforming elec- tricity. By throwing a small lever, the outgoing current can be varied from fifty to more than a million vibrations a second.

��the prohibitive cost. Music from elec- tricity — or music from light, to be exact— goes back many years before the telharmonium. Legendary Egyp- tian history, three thousand years old, tells us that the rays of the descending sun, would strike w^eird music from the face of the statue of Memnon. Incredible as this tale may seem to

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