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.

It should be noted here that sunlight, as we call it, is accompanied by heat.

By means of valves the proportions of the gases can be regulated to give the best results.

This difficulty Helmholtz gets over by suggesting that in such an ear two adjacent fibres are affected, but one more than the other.

There are, so to speak, minor hills and valleys cut in the slopes of the main hills and valleys.

Moisture then passes from the walls and objects in the room to the atmosphere.

The action of the pump will be easily understood from the diagram.

The introduction of the electric arc lamp and the incandescent glow-lamp seemed at one time to spell the doom of gas as an illuminating agent.

he adoption of the going-barrel has been made satisfactory by the improvements in the various escapement actions.

The chances therefore were greatly against a wrong key turning the lock.

The carter makes use of this principle when he puts his hand to the top of a wheel to help his cart over an obstacle.

Through slots in these the cutter-bar works, and its knives give a drawing cut to grass caught between them and the sides of the spikes.

This explains why high tide occurs at intervals of more than twelve hours.