What is a Phonograph?

It is an instrument for recording the vibrations of sounds, and consists of a revolving cylinder covered with tin-foil.  To this cylinder is attached a mouth-piece, fitted with a thin plate or disk, on the outer side of which, next to the cylinder, is a needle or point.  The cylinder runs on a screw, so that the whole length of it, from end to end, may pass under the point.  On speaking into the mouth-piece the voice causes the disk to vibrate, and the point to trace marks corresponding to these vibrations on the tin-foil.  By turning the cylinder so that the point again passes into the marks in the tin-foil, the sounds that entered at the mouth-piece can be reproduced at any time.

By whom was the phonograph invented?

By Thomas A. Edison, who was born in Ohio in 1847.  Mr. Edison is the inventor of many improvements in telegraphy, which have been adopted into general use, and are to him the source of a large income.  To him, also, we are indebted for the megaphone, microphone, tasimeter, an improvement in the telephone, a system of electric lighting, and many other inventions.

What is a Microphone?

This instrument is a variety of telephone by means of which faint sounds can be heard at a very great distance.  It consists of a small battery for generating a weak current of electricity, a telephone for the receiving instrument, and a speaking or transmitting instrument.  The last is a small rod of gas carbon with the ends set loosely in blocks of the same material.  The blocks are attached to an upright support, glued into a wooden base board.  This instrument is connected with the battery and the telephone.  So wonderfully sensitive is it, that the ticking of a watch, the walking of a fly across a board, or the brush of a camel’s-hair pencil can be heard even though it be hundreds of miles distant.

Will you describe the Megaphone?

It is a substitute for the ear and speaking trumpet.  It consists of three paper funnels placed side by side.  The two larger ones are about 6 feet 8 inches long and 27-1/2 inches in diameter, and are each provided with a flexible tube, the ends of which are held to the ear.  The centre funnel, which is used as a speaking-trumpet, does not differ materially from an ordinary trumpet, except that it is larger and has a larger bell mouth.  Two persons, each provided with a megaphone, can, without other apparatus, carry on a conversation at a distance of one and a half or two miles.

What is the Tasimeter?

It is an instrument, sensitive to the smallest degree of heat, and is mostly used in astronomy.  Attached to a telescope it will show the heat coming from the stars.

What is a Bathometer?

This ingenious instrument, the invention of Prof.  Siemens of London, enables those on board of ships to read from an index the depths of the ocean beneath them.  It consists of a highly sensitive steel spring to which a heavy piece of metal is attached.  The changes in weight to which the latter is subject in consequence of the variations of attractive force (the deeper the ocean the smaller the latter, and vice versa) are registered on a scale by the indicator that is in connection with the steel spring.