"It seems simple enough," speculated Laurie.

"It was not so simple to carry out," declared Mr. Hazen. "Of course, as I told you, Mr. Bell could not give his entire time to it. He had his teaching both at Boston University and elsewhere to do. Nor was he wholly free at the Saunders's, with whom he boarded at Salem, for he was helping the Saunders's nephew, who was deaf, to study."

"And in return poor Mrs. Saunders had to offer up her piano for experiments, I suppose," Ted observed.

"Well, perhaps at first—but not for long," was Mr. Hazen's reply. "Mr. Bell soon abandoned piano strings and in their place resorted to flat strips of springy steel, keying them to different pitches by varying their length. One end of these strips he fastened to a pole of an electromagnet and the other he extended over the other pole and left free."

"And the current interrupters?" queried Ted.

"Those current interrupters are the things which have since become known as transmitters," explained Mr. Hazen. "Those Mr. Bell made all alike except that in each one of them were springs kept in constant vibration by a magnet or point of metal placed above each spring so that the spring would touch it at every vibration, thus making and breaking the electric current the same number of times per second that corresponded to the pitch of the piece of steel. By tuning the springs of the receivers to the same pitch with the transmitters and running a wire between them equipped with signalling keys and a battery, Bell reasoned he could send as many messages at one time as there were pitches."

"Did he get it to work?" Laurie asked.

"Mr. Bell didn't, no," replied the tutor. "What sounded logical enough on paper was not so easy to put into practise. The idea has been carried out successfully, however, since then. But Mr. Bell unfortunately had no end of troubles with his scheme, and we all may thank these difficulties for the telephone, for had his harmonic telegraph gone smoothly we might not and probably would not have had Bell's other and far more important invention."

"The discovery of the telephone was a 'happen,' then," Ted ventured.

"More or less of a happen," was the reply. "Of course, the intelligent recognition of the law behind it was not a happen; nor was the patient and persistent toil that went into the perfecting of the instrument a matter of chance. Alexander Graham Bell had the genius to recognize the value and significance of the truth on which he stumbled and turn it to practical purposes. Many another might perhaps have heard the self-same sounds that came to him over that reach of wire and, detecting nothing unusual in the whining vibrations, have passed them by. But to Mr. Bell they were magic music, the sesame to a new country. Strangely enough, too, it was the good luck of a boy not much older than Ted to share with the discoverer the wonderful secret."