excellent weekly publication, La Lumière Électrique;1 for the account of the Edison system I am indebted to Mr. Dredge's book on Electric Illumination.

Chapter IV. of the first volume, containing the applications of electric light, is entirely new, and is also for the most part taken from La Lumière Électrique.

Part II. of the second volume, which treats of the "Various Applications of Electricity," has been added nearly in its entirety; as also the third part, which gives an account of Marcel Deprez's interesting researches and successful experiments on electrical transmission of energy.

I have to thank Messrs. Crompton, Lane Fox, Lever, McEvoy, Swan, the Brush Company, and the Pilsen and Joël Company, for their great kindness in supplying me with information and illustrations of their respective apparatus; and also the editors of the Engineer and the Electrician for the loan of blocks illustrating the Edison machine, Brown and Saunders' telephone system, and the Ferranti machine. I am also under great obligation to my friend, Mr. J. E. Julian, of the Inner Temple, for looking over the proofs.

CHELTENHAM,

July, 1883.

In addition to the Figures described in the text as having been taken from La Lumière Électrique, the following are also from the same source:Figs. 6, 54 to 62, 70, 71, 73, 74, 76 to 80, 86, 93 to 96.

UNITE SIT

CAL

THE MODERN APPLICATIONS

OF

ELECTRICITY.

PART I.

THE SOURCES OF ELECTRICITY.

THE first electric phenomenon is mentioned by Thales of Miletus, who observed, 600 B.C., that amber, after being rubbed, acquired the property of attracting light bodies; but Otto de Guéricke, towards the middle of the seventeenth century, was the first to observe the electric spark.

The identity of lightning and electricity was not demonstrated until a century later, in 1752, by the illustrious Franklin; and fifty years after that, Volta inaugurated, by the construction of the electric pile, a new era in the history of electricity, the field of which has been so immensely widened during the last few years.

The whole of the eighteenth century is full of studies and discoveries in statical electricity, and it was reserved for Volta to lay the foundation of the numerous discoveries in dynamical electricity. This distinction has almost disappeared, and we shall see in the following chapters how the so-called statical electricity is changed into dynamical electricity, and vice versâ.

From the point of view of practical application-the only VOL. I.

B

part of electricity which interests us in this work-the electrical machines (friction machines, etc.) have given no results, and the high-tension currents which they give have only been used for amusing experiments, for lecture purposes, and for purely scientific research.

We shall, therefore, not consider them, but refer our readers to the treatises on elementary physics, where they will find these phenomena described at length. We are solely concerned with the different modes for producing so-called dynamical electricity, and with its principal applications.

Before proceeding to this, our special task, it will not be out of place to say a few words concerning the modern views on the nature of electricity itself.

Whatever may be the exact nature of electricity, it is now regarded chiefly as a medium for the transmission of force; or, more properly, of kinetic energy.

Some physicists regard electricity as a peculiar vibration of what corresponds to the luminiferous ether (a highly attenuated fluid pervading all matter). It is probable that electrical induction is due to some such vibration. The late Professor Clerk Maxwell has investigated the subject very fully, his enquiries going far to prove that if electrical induction is due to a vibration of the luminiferous ether itself, the vibration is such, that the waves undulate in a plane at right angles to those of light and heat.

An electric current is probably nothing more than the actual transference of this "ether" through a conducting material—that is to say, a material through which it can be made to pass without meeting with any great resistance. The difference between electricity and an electric current may be likened to that between air at rest and air in motion.