CHAPTER I.-HISTORICAL AND DESCRIPTIVE.

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Sir Humphrey Davy - Electric light first produced chemically -
Faraday's discovery of electro-magnets, and thereby of mechanical pro-
duction of electric light-Machines of Pixii, Clark, and Nollet, leading
to those of Holmes and of the Alliance Company, in use in English and
in French lighthouses - Principle of reaction between electro-magnets
- Magneto-electric and dynamo-electric machines Single-light and
many-light machines - Commutators Continuous and alternating-
direction currents - Experiments at South Foreland by Trinity House
- Experiments of Franklin Institute at Philadelphia

CHAPTER II.-ELECTRIC-LIGHT MACHINES.

Magneto-electric: Holmes, Alliance, De Meritens — Dynamo-electric:
Siemens, Gramme, Wilde, Wallace-Farmer, Brush, Lontin, Gramme
(dividing), Siemens (dividing)

CHAPTER III.-LAMPS AND REGULATORS.

General duties and requirements - Voltaic arc- - Incandescence.
Regulators: Serrin, Siemens, Lontin, Rapieff, Wallace, Reynier, Werder-
Candles: Jablochkoff, De Meritens, Wilde, Rapieff

mann -

CHAPTER IV.-CARBONS-CONDUCTING WIRES.

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Carbons: Natural, cut out of graphite deposit—Artificially prepared —

Metallized Conducting wires: Continuous and alternating-direction

currents-Examples-Differences in practice-Question still open for

inquiry.

CHAPTER V.-MOTIVE POWER.

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Steam, gas, water, &c. - Extreme regularity requisite - Special engine,

not doing other work- Rate of speed-Estimate, as generally stated, too

low-Power absorbed by electric machine, and also gross power required

- Comparison of results with different machines.

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50

CHAPTER VI.-LUMINOUS INTENSITY.

Light produced varies with nature of current and with form of lamp

--Continuous current: Gramme, Siemens-Alternating current: Alliance,

Lontin, Jablochkoff-Actual illumination — Conditions of preference

-Photometric measurements - Clear understanding required - Photo-

meters of Bunsen, Rumford, and Wheatstone-Standard of comparison.. 59

CHAPTER VII.-APPLICATIONS-ECONOMIC RESULTS.

South Foreland, Souter Point, Lizard, and Cape La

Hève Lighthouses. Northern of France Ry., Powell,

and Albert Hall.

Lyons Ry., Western of France Ry., and Gaiety

Theatre, London.

Avenue de l'Opéra, Thames Embankment, Holborn

Viaduct, Billingsgate Market.

'Times' Office.

Wallace-Farmer, Liverpool Street Station, London.

Economic result afforded by effective illuminating power in proportion

to working cost — Comparison of different examples - Effect of sub-
division of the light — Table of working of different machines .

74

CHAPTER VIII.-PROSPECTS OF ELECTRIC LIGHTING.

-

Practical solution only effected for certain cases Solution of remainder

of problem - Difficulties to be removed. Too much at present expected

from electric light- Comparison of cost of production of electric light at

retail price with that of gas at wholesale price, not a fair one - Sanitary

aspect-Ultimate distribution of electric lighting-Tendency to a more

powerful illumination from whatever source

101