been connected with the binding posts _d_ and _e_ of the relay. [Illustration: Fig. 190] The chandelier over the dining-room table had a pendant push button _A_ (Fig. 191), with which the regular electric lights could be turned on and off. This I had removed and extended the wires down upon the table. It was only necessary to connect these to the binding posts _d_ and _e_ of the relay, and the next wave from the spark coil lighted the chandelier. [Illustration: Fig. 191] The flexible wires underneath the dining-room table with which the maid is usually summoned from the kitchen were next extended up and connected with _d_ and _e_ of the relay, and the maid was called in by an ether wave. She brought with her a tray in the centre of which stood an earthenware cup, such as is used for baking custard. This had been filled with a mixture of granulated sugar and powdered potassium chlorate. Four dry battery cells stood around this upon the tray connected in series (Fig. 192). A very small iron wire connecting two of these cells dipped into the sugar mixture. Two wires from the battery were connected to _d_ and _e_ of the relay. At the proper signal an ether wave was sent out by the spark coil. The coherer closed the relay and the relay acted as a push button to close the circuit of the four cells upon the tray. The fine wire dipping into the sugar and potassium chlorate got red hot. This caused the mixture to flash up and burn in most beautiful coloured flames. (Fig. 193). [Illustration: Fig. 192] [Illustration: Fig. 193] On this occasion Harold's friends gave him, with due formalities, the degree of E. E., which they said meant _electrical expert_, and ever since that night he has been called "the expert." I inquired of the young folks, as their party was breaking up, if they understood Harold's explanations of all these things, and he replied that he at any rate understood them better having attempted to explain them. XXIII TELEGRAPHING BY ELECTRIC WAVES The next time Harold and I experimented we arranged something to save us the trouble of tapping the coherer each time we used it. We employed simply an electric bell, _B_ (Fig. 194), from which we removed the gong. By reference to the figure the arrangement will be understood. Each time ether waves cause the metal filings to cohere and the battery _B^{1}_ closes the relay _R_, battery _B^{2}_ causes the hammer of _B^{3}_ to tap against the coherer. This causes the current to cease to flow from _B^{1}_ and the relay opens again by its own spring. [Illustration: Fig. 194] [Illustration: Fig. 195]