Evidently, Mr. Edison said to himself:  “The telephone hears and speaks; why not make it write in its own way; then its record could be kept, and any time after, the instrument might read aloud its own writing.”  Like a great genius as he is, Mr. Edison went to work in the simplest way to make the sound-recorder he wanted.  You know how the diaphragm of the telephone vibrates when spoken to?  Mr. Edison took away from the telephone all except the mouth-piece and the diaphragm, fastened a point of metal, which we will call a “style,” to the center of the diaphragm, and then contrived a simple arrangement for making a sheet of tin-foil pass in front of the style.  When the diaphragm is still, the style simply scratches a straight line along the foil.  When a sound is made, however, and the diaphragm set to vibrating, the mark of the style is not a simple scratch, but an impression varying in depth according to the diaphragm’s vibration.  And that is how the phonograph writes.  To the naked eye, the record of the sound appears to be simply a line of pin points or dots, more or less close to each other; but, under a magnifier, it is seen to be far more complicated.

Now for the reading.  The impression on the foil exactly records the vibrations of the diaphragm, and those vibrations exactly measure the sound-waves which caused the vibrations.  The reading simply reverses all this.  The strip of foil is passed again before the diaphragm, the point of the style follows the groove it made at first, and the diaphragm follows the style in all its motions.  The original vibrations are thus exactly reproduced, setting up sound-waves in the air precisely like those which first set the machine in motion.  Consequently, the listener hears a minutely exact echo of what the instrument heard; it might have heard it a minute, or an hour, or a year, or a thousand years before, had the phonograph been in use so long.

What a wonderful result is that!  As yet, the phonograph has not been put to any practical use; indeed, it is scarcely in operation yet, and a great deal must be done to increase the delicacy of its hearing and the strength of its voice.  It mimics any and every sort of sound with marvelous fidelity, but weakly.  Its speech is like that of a person a long way off, or in another room.  But its possibilities are almost infinite.

ONLY A DOLL!

BY SARAH O. JEWETT.

[Illustration:  “Polly, my dolly!”]

  Polly, my dolly! why don’t you grow? 
        Are you a dwarf, my Polly? 
  I’m taller and taller every day;
    How high the grass is!—­do you see that? 
  The flowers are growing like weeds, they say;
    The kitten is growing into a cat! 
        Why don’t you grow, my dolly?

  Here is a mark upon the wall. 
        Look for yourself, my Polly! 
  I made it a year ago, I think. 
    I’ve measured you very often, dear,
  But, though you’ve plenty to eat and drink,
    You haven’t grown a bit for a year. 
        Why don’t you grow, my dolly?