he spindle has made a half revolution, bringing B in contact with G, and C with F. But by this half turn the current is reversed in the bobbins, and the + current flows into C, through F, to terminal H as before, and through the circuit to K, through G and B, back to the bobbins. Thus you see that in the circuit the current will be always in the same direction, or continuous, although in the bobbins it is alternating, and may be used for any purpose for which a continuous current is required, such as electro-plating, &c.
[Illustration: FIG. 4.]
There are various forms of the magneto-electric machines, as well as of commutators, but the foregoing shows the general principle of them all.
It will now be necessary to explain the nature of a dynamo-electric machine, called, for shortness, a dynamo, and to show in what it differs from a magneto-electric machine.
I have explained how an electric current is produced by a wire passing in front o