tofore, and
without variation; but this evening Angel startled himself, as he did
the others, by actually sounding two additional notes. He repeated this
over and over.

"I wonder if we could make him talk?" asked George, after the laughter
had subsided.

"There is no reason why some tones cannot be imitated. As the orang
possesses wonderful powers of imitation and has, in captivity, developed
many traits, I see no reason why simple words, or sounds, cannot be
taught."

"I know there are words which he does understand. Time and again I have
told him things, which he seems to understand. Now see if he understands
this: 'Angel, do you want some honey?'"

His attempts at whistling ceased, and in a moment more was in the
kitchen. Harry, who by this time had recovered from his mirth, thought
it would be a good idea to attempt to teach him.

"If canary birds and dogs can understand language, I do not see why
Angel shouldn't."

"Unquestionably, any animal, by patience, will learn the meaning of
sounds. Constant repetition of certain notes causes birds to repeat
them. I have known dogs to perform almost anything they were told to do,
although they are not able to utter a single sound of the words emitted
in giving the command."

"Well, what is it that causes sound?"

"The most wonderful thing in nature is, that she manifests herself in
only one way, namely, by a movement, or a motion of some kind. Vibration
is the term used to designate this. Sound, light, heat, taste, smell,
and everything which becomes sensible to us is produced by vibration.
The movements of the heavenly bodies, swinging back and forth around the
sun, like huge pendulums, the movement of the sap in trees, up and down,
the beating of the heart, the winking eyelids are all motions which show
energy, development, life."

"But what is it that makes us understand one sound from the others?"

"Simply the difference in the kind of vibration. There are three things
which characterize sounds; namely, pitch, intensity and character. Pitch
depends on the rapidity of the vibrations; intensity on the extent or
the amplitude of the vibrations; and character on the substance or
instrument producing them. To illustrate: When you sing a very high note
the vibrations may be five thousand vibrations a second, or there may be
only two thousand during that time. That represents the pitch. In
singing that note you may sing it so loud that, like a pendulum, it will
s