: The Salving of the Fusi Yama: A Post-War Story of the Sea by Westerman Percy F Percy Francis Hodgson E S Edward Smith Illustrator - Sea stories; Treasure troves Juvenile fiction; Warships Salvaging Juvenile fiction

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THE ELECTRIC CURRENT, AND ITS PRODUCTION BY CHEMICAL MEANS. PAGE

Production of electric current in chemical battery--Current very weak--Current compared to circulation of the blood--Strength and volume of current--Pressure not sufficient without volume--Action of current is instantaneous--Resistance to the passage of the current--Copper the usual metal for conductors--Heat produced by current when wire is too small 1

PRODUCTION OF ELECTRIC CURRENTS BY MECHANICAL MEANS.

Current produced by mechanical means--Alternating current-- Magneto-electric machines--Shock produced by interruption of current--The current must be commutated--Description of commutator--Current, though alternating in the dynamo, is continuous in the circuit--Continuous current used for electro-plating 5

Current will magnetise an iron or steel bar--Permanent magnet-- Electro-magnet--Where the magneto and dynamo machines differ-- Armature of so-called continuous-current dynamo--Type of commutator--Commutator brushes--Current continuous in the circuit--Alternating-current dynamos--Current not commutated-- Intense magnetic field produced--Simplicity of Ferranti armature-- Large number of alternations of the current--Alternating current cannot be used to excite an electro-magnet--Exciter coupled on to same spindle as dynamo--Power of exciter if used alone 9

ELECTRIC LAMPS.

Production of electric light--Arc lights--Mechanism to regulate carbons--Some lamps suitable for alternating current--When carbons are consumed, light goes out--Arc lamps very complicated-- Jablochkoff candles--Arc formed between the carbons--Candles require alternating current--Incandescent lamps--Vacuum formed in lamps prevents combustion--Vacuum not perfect--Advantages of incandescent lamps for house and ship lighting--Unaffected by wind, and suitable for either continuous or alternating currents 19

LEADS.

Leads made usually of copper wire--Short circuit--High E.M.F. for arc lights, but low for incandescent--Arc lights in series-- Incandescent lamps in parallel circuit--E.M.F. same for one lamp as for a number--If lamps suitable, each one turns on and off separately--Safety fuses 24

SHIP LIGHTING.

Position for dynamo--Dynamo to be kept clean and cool--Quick-speed engines--Slow-speed engines with belts--Means of keeping belt on the pulley--Engine must work steadily--A good sensitive governor wanted--The belt must be kept tight--A handy belt-stretcher-- Friction gearing--Switch board near dynamo--Leads of different colours--Main leads and branch leads--Lamps held in frosted globes--Switches for each lamp--Lamps of various candle-powers-- Plan for lighting quarter-deck at times--Arrangement of temporary leads--Leads and lamps always ready, and easily fixed up--Lighting of ships' holds--Danger of fire with oil lamps--Arc lamps not suitable--Arrangement of leads for incandescent lamps-- Work carried on better, and pilfering of cargo prevented--Hold leads disconnected while at sea--Installation complete--Lights wanted as night approaches--Precautions before starting dynamo-- Lubrication must be perfect--Commutators and collectors require very little oil--Position of brushes--Start the engine--Switches not turned on; no current except from exciter--Testing work of exciter--Dynamos very powerful magnets--Look out for your watches--Switch on the lamps--Current is produced in large dynamo-- Difference of a few lamps compensated by governor--Turn all lamps on, and light up gradually--Inequality of light in different lamps--Weeding out of bad lamps--Lamps not to be run too bright-- No trouble with dynamo if oiling is attended to--Seizing--Oil must be thin--The dynamo must be kept clean--Little troubles with the lamps--No safety fuse--Effects of vibration of ship on lamps-- What to look to if a lamp is out.--Recapitulation--A current of 50 volts is hardly felt--Incandescent lights for side lights-- Mast-head light--Arc light should never be used--Present mast-head light quite powerful enough--On passenger steamers, side one blaze of light, and side lights barely visible--Speed of dynamo constant, but steam power used in proportion to number of lamps in use--No danger to life from electric current on board ship-- Binnacle lamps. Electric light not suitable--Dynamo if near a compass will affect it--Notes 27

WRINKLES IN ELECTRIC LIGHTING.

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