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. 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. [Illustration: Fig. 199] 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. [Illustration: Fig. 200] In 1819 Hans Christian Oersted in Denmark (1777-1851) first noted that the region about a wire carrying an electric current has an influence upon a magnet. I will show this fact by a simple experiment. I magnetize a stout sewing needle by drawing it from end to end across the pole of a steel magnet, and by means of a triangular piece of paper and a fine thread I suspend it a few inches above the table (Fig. 200). I then lay upon the table a piece of wire parallel with the needle and fasten one end of it to one binding post of a dry cell. Whenever I touch the other end of the wire to the other binding post of the cell, thus sending an electric current through the wire, the magnetized needle is deflected at right angles. This experiment, performed by Oersted, seems to have started Faraday upon that wonderful series of researches which has resulted in giving us the dynamo. XXVII WIRELESS TELEGRAPHY IN EARNEST