Fig. 6.—Connection of microphone and telephone.
By attaching one receiver and the battery to the microphone as shown in [Fig. 7], very slight sounds will be increased to an extraordinary degree. The ticking of a watch seems like so many heavy footfalls, and if you can succeed in getting a fly to walk across the sounding-board, as the base is called, the footsteps will be plainly heard. Many interesting experiments can be performed in this manner, and as the microphone is so easily made, it is well worth constructing one for the sake of such experiments alone.
Fig. 7.—Experiment with microphone.
CHAPTER L
TELEGRAPHY AT HOME
A Galvanometer Adapted
Like most of the inventions that have revolutionized the world, the electric telegraph is constructed upon the simplest principles.
As will be shown, an instrument for transmitting and receiving messages can easily be made at a very small cost by any one prepared to devote a little care to its construction; and when completed it will be found of considerable use and convenience.