When the utterance which is to be reproduced has been completed, the instrument is stopped, the stylus thrown back from the groove, and the cylinder revolved backward to the place of starting.  The stylus is then returned to its place in the groove, and the cylinder is revolved forward at the same rate of rapidity as before.  As the point of the stylus plays up and down in the indentations and through the figures in the tin-foil, produced by its own previous agitation, a quiver exactly equivalent to that which was produced by the utterance in the mouth-piece is thrown into the air.  This agitation is of course the exact physical equivalent of the original sound, or, more properly, is the sound itself.  Thus it is that the phonograph is made to talk, to sing, to cry; to utter, in short, any sound sufficiently powerful to produce a perceptible tremor in the mouth-piece and diaphragm of the instrument.

Much progress has been made toward the utilization of the phonograph as a practical addition to the civilizing apparatus of our time.  It may be said, indeed, that all the difficulties in the way of such a result have been removed.  Mr. Edison has carried forward his work to such a degree of perfection that the instrument may be practically employed in correspondence and literary composition.  The problem has been to stereotype, so to speak, the tin-foil record of what has been uttered in the mouth-piece, and thus to preserve in a permanent form the potency of vanished sounds.  Nor does it require a great stretch of the imagination to see in the invention of the phonograph one of the greatest achievements of the age—­a discovery, indeed, which may possibly revolutionize the whole method of learning.

It would seem clear that nature has intended the ear, rather than the eye, to be the organ of education.  It is manifestly against the fitness of things that the eyes of all mankind should be strained, weakened, permanently injured in childhood, with the unnatural tasks which are imposed upon the delicate organ.  It would seem to be more in accordance with the nature and capacities of man, and the general character of the external world, to reserve the eye for the discernment and appreciation of beauty, and to impose upon the ear the tedious and hard tasks of education.

The phonograph makes it possible to read by the ear instead of by the eye, and it is not beyond the range of probability that the book of the future, near or remote, will be written in phonographic plates and made to reveal its story directly to the waiting ear, rather than through the secondary medium of print to the enfeebled and tired eye of the reader.

We hardly venture on prophecy; but we think that he who returns to this scene of human activity at the close of the twentieth century will find that sound has been substituted for sight in nearly everything that relates to recorded information, to learning, and to educational work.  By that means the organ of hearing will be restored to its rightful office.  Enlightenment and instruction of all kinds will be given by means of phonographic books.  The sound-wave will, in a word, be substituted for the light-wave as the vehicle of all our best information and intercourse.  The ear will have habitually taken the place of the eye in the principal offices of interest and information.