The Sciences, Illustrated Edition (Yesterday's Classics) by Holden Edward S

Author:Holden, Edward S. [Holden, Edward S.]
Language: eng
Format: epub
Tags: Nature
ISBN: 9781599153384
Publisher: Yesterday's Classics
Published: 2010-11-10T01:56:03.521000+00:00

THE VOCAL CHORDS

THE PHONOGRAPH.—Jack. The phonograph is a machine for recording the vibrations of the air that are made when a person speaks. He speaks into a tube and sets the air into vibration. At the small end of the tube is a little round thin metal plate called a diaphragm that moves up and down (slightly) as the air vibrates. The motions of this little plate copy the vibrations of the air. On the lower side of this thin plate is a sharp needle point. The point of the needle is in contact with a smooth wax surface which is moved under the point as a disk record is moved in the phonograph. The needle cuts a groove in the wax. If the diaphragm vibrates, moving the needle up and down, the depth of the groove varies in accordance with the vibrations. In some types of instruments the needle moves sideways instead of up and down. The soft records are copied in harder materials for sale as the familiar phonograph records.

Tom. If the phonograph had been invented in Julius Caesar's time, we might be able to hear his voice now, or George Washington's, or Lincoln's.

Jack. The records of the speeches of some of the great men of to-day actually have been preserved; and long after they are dead, other people will know exactly how they spoke.

Mary. It would be a find thing for us to get Eleanor to sing into the phonograph now, so that when we go home after vacation we could still hear her!

Jack. A wise man in England 19 once suggested that there could be no worse punishment in a future life than to be forced perpetually to hear all the foolish things you had said in this life. It might not be a bad way to punish naughty boys and girls in this world to shut them up in a room with phonographs that would continually repeat the silly and foolish things they had said.

Agnes. I think it would be dreadful, Jack. Nothing could be worse.

Jack. Very well, my dear, you need not mind. The things you say are always nice to hear. I was only trying to frighten the boys.

ELECTRICITY—The children made some experiments in electricity which any one of you can make too, if you like. You will need a few things, most of which you can get at home or make for yourself. A few you will have to buy (they do not cost much). The principal things to get are: a couple of toy magnets, one straight, one shaped like a horseshoe; a piece of glass tube (or a glass rod) about half an inch in diameter and eight or ten inches long; a piece of sealing wax about half an inch square and about six inches long; a rubber comb; an old silk handkerchief; a piece of old flannel; an ounce of sulphuric acid in a bottle with a glass stopper (be careful not to get the acid on your

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