Laurie, Ted, and Mr. Hazen were in the shack on a Saturday afternoon
not long after the adventure on the river. A hard shower had driven
them ashore and forced them to scramble into the shelter of the camp at
the water's edge. How the rain pelted down on the low roof! It seemed
as if an army were bombarding the little hut! Within doors, however,
all was tight, warm, and cosy and on the hearth before a roaring fire
the damp coats were drying.

In the meantime the two boys and the young tutor had dragged out some
coils of wire and a pair of amateur telephone transmitters which Ted
had concocted while in school and for amusement were trying to run from
one end of the room to the other a miniature telephone. Thus far their
attempts had not been successful and Ted was becoming impatient.

"We got quite a fair result at the laboratory after the things were
adjusted," commented he. "I don't see why we can't work the same stunt
here."

"I'm afraid we haven't put time enough into it yet," replied Mr. Hazen.
"Don't you remember how long Alexander Graham Bell, the inventor of the
telephone, experimented before he got results?"

Laurie, who was busy shortening a bit of wire, glanced up with
interest.

"I can't for the life of me understand how he knew what he wanted to
do, can you?" he mused. "Think of starting out to make something
perfectly new--a machine for which you had no pattern! I can imagine
working out improvements on something already on the market. But to
produce something nobody had ever seen before--that beats me! How did
he ever get the idea in the first place?"

The tutor smiled.

"Mr. Bell did not set out to make a telephone, Laurie," he answered.
"What he was aiming to do was to perfect a harmonic telegraph, a scheme
to which he had been devoting a good deal of his time. He and his
father had studied carefully the miracle of speech--how the sounds of
the human voice were produced and carried to others--and as a result of
this training Mr. Bell had become an expert teacher of the deaf. He was
also professor of Vocal Physiology at Boston University where he had
courses in lip reading, or a system of visible speech, which his father
had evolved. This work kept him busy through the day so whatever
experimenting he did with sounds and their vibrations had to be done at
night."

"So he stole time for electrical work, too, did he?" observed Ted.

"I'm afraid that his interest in sound vibration caused him a