Harold said that if electricity was so much like light that it could go without wires he thought light ought to be enough like electricity to be conducted by wires on occasions. I told him that I had no hope of being able to confine light to a wire; indeed, if the Science Club would give me an opportunity I would show them that even when electricity follows the general direction of a wire its influence is not confined to the wire. As a result of this bid I received an invitation to address an open meeting of the Science Club.
Fig. 198
In my first experiment on that occasion I took a one-pound spool of No. 24 cotton-covered copper wire and crowded the hole in the spool full of wire nails A ([Fig. 198]). I disconnected the wires from an electric drop lamp and connected them to b and c, the ends of the wire from the spool. Our electric lighting circuit was what is called the alternating current. I also had a second spool, B, precisely like the first. The wires from this were connected to a miniature lamp, L, such as is used at the switchboard of a telephone exchange. We then screwed the drop-light plug into the chandelier and turned on the electric current. I brought spool B with the miniature lamp near to spool A, as shown in [Fig. 199], and when it was within a distance of about two inches the little lamp lighted up to full brilliancy, thus showing that while the electric current is passing in the wire of spool A its influence is not confined to the wire, but exhibits itself in the region outside of the wire. To illustrate still further this fact we substituted an electric bell in the place of the lamp L, and when the spool B was brought near to A the bell rang. But the most striking illustration was obtained when a telephone receiver was put in the place of L. With this held to the ear while the spool B was brought toward A a humming sound could be heard when B was about a foot distant from A. This sound grew rapidly louder as B approached A, until, when the spool B rested upon the spool A, a sound like the peal of a pipe organ was heard all over the apartment. The tone was very nearly that of the key on the piano which is two octaves below middle C. I unscrewed the cap on the large end of the telephone receiver, took it off, and moved the thin iron diaphragm to one side, when it began to dance about at great speed. It was keeping time with the dynamo, five miles away, which generated the electric current. The dynamo changed the direction of the electric current sixty times per second, and this made sixty vibrations per second. The dynamo sent out ether waves which affected the telephone receiver, although the receiver was not connected to the dynamo by wires.
Fig. 199
To emphasize the fact that the dynamo had lighted the lamp, rung the bell and made the telephone receiver hum without being connected with them, I repeated all these experiments in a different way. Spool A, connected as before with the electric lighting circuit, was concealed beneath the table. For spool B I substituted spool C ([Fig. 199]), on which the wire was wound so as to appear like a candlestick. On the top of this was placed the miniature electric lamp screwed into a miniature socket and connected to the wires of the spool. This "Witches' Candle," as we called it, was sitting unlighted upon the table when I called attention to the fact that if I moved it to a certain spot upon the table it flashed into full light. (Of course this spot was directly over spool A.) I moved it slowly away from that spot and its light slowly grew dim and disappeared.
On the table was also sitting a cream pitcher in which I had placed spool B with a buzzer attached to it. Remarking that this pitcher groaned for more cream whenever it was empty, and thus of its own accord called the waiter, I moved it to the spot on the table directly over spool A, when the buzzer gave forth a sound like a husky bumble-bee shut up in a resounding bottle. At this signal my assistant came in and took up the pitcher and placed my silk hat upon the table, when it instantly boomed forth a base note two octaves below middle C of the piano. Out of the hat I took a coil and the telephone receiver and the mystery was solved.