sorry
loss of sleep," said the tutor. "But certainly his later results were
worth the amount of rest he sacrificed. One of the first agencies he
employed to work upon was a piano. Have you ever tried singing a note
into this instrument when the sustaining pedal is depressed? Do it some
time and notice what happens. You will find that the string tuned to
the pitch of your voice will start vibrating while all the others
remain quiet. You can even go farther and try the experiment of
uttering several different pitches, if you want to, and the
corresponding strings will give back your notes, each one singling out
its own particular vibration from the air. Now the results reached in
these experiments with the piano strings meant a great deal more to
Alexander Graham Bell than they would have meant to you or to me. In
the first place, his training had given him a very acute ear; and in
the next place, he was able to see in the facts presented a
significance which an unskilled listener would not have detected. He
found that this law of sympathetic vibration could be repeated
electrically and, if desired, from a distance by means of
electromagnets placed under a group of piano strings; and if afterward
a circuit was made by connecting the magnets with an electric battery,
you immediately had the same singing of the keys and a similar
searching of each for its own pitch."

"I'd like to try that trick some time," exclaimed Ted, leaning forward
eagerly.

"So should I!" echoed Laurie.

"I think we could quite easily make the experiment if Laurie's mother
would not object to our rigging up an attachment to her piano," Mr.
Hazen responded.

"Oh, Mater wouldn't mind," answered Laurie confidently. "She never
minds anything I want to do."

"I know she is a very long-suffering person," smiled the tutor. "Do you
recall the white mice you had once, Laurie, and how they got loose and
ran all over the house?"

"And the chameleons! And the baby alligator!" chuckled Laurie. "Mother
did get her back up over that alligator. She didn't like meeting him in
the hall unexpectedly. But she wouldn't mind a thing that wasn't
alive."

"You call an electric wire dead then," said Ted with irony.

"Well, no--not precisely," grinned Laurie. "Still I'm certain Mater
would be less scared of it than she would of a mouse, even if the wire
could kill her and the mouse couldn't."

"Let's return to Mr. Bell and his piano strings," Ted remarked, after