In some condensers the positions of steam and water are reversed, steam going through the tubes outside which cold water circulates.

Under ordinary conditions these turbines revolve idly in their cases.

As soon as the engine begins to fire, the faces of the clutches slip over one another.

There will be more to say about transformation of current in later paragraphs.

Messages have been transmitted by this system at the rate of 180,000 words per hour.

By adjusting the receiving circuit to the transmitter, or vice versâ, selective wireless telegraphy becomes possible.

The galvanometer is affected like the coils and small magnet in Wheatstone's needle instrument.

Anybody who understands the dynamo will also be able to understand the electric motor, which is merely a reversed dynamo.

The action of these brakes will now be explained as simply as possible.

The last is sometimes reinforced by an "advance starting" signal some distance farther on.