The Story of Electricity

practical uses. Of these by far the most important are based on its property of developing light and he

The strength of the current or quantity of water flowing per second is greater the higher the pressure, and the less the resistance of its channel. The power of the water or its rate of doing mechanical work is greater the higher the pressure and the stronger the current. So, too, electricity flows by the electromotive force from a place of higher to a place of lower electric level or potential. The

a large quantity at a low pressure, and our choice of one or the other will depend on the purpose we have in view. As

fluence machine can be compared to a highland cataract of lofty height but small volume, which is more picturesque than useful, and the current from a voltaic

nd hence the voltaic battery or a special form of dynamo is usually employed in this work. A flash of lightning is the very symbol of terrific power, and

chemical for decomposition, a telegraph instrument, an electric lamp, or any other appliance. As the current in the race depends on the "head of water," or difference of level between the dam and the sea as well as on the resistance of the channel, so the current in the circuit depends on the "electromotive force," or diff

ans. Thus the unit of quantity is the coulomb, the unit of current or quantity flowing per second

ional to the strength of the current. One ampere decomposes .00009324 gramme of water

e electrochemical equivalent of the ion. This is found by multiplying its ordinary chemical equivalent or combining weight by .000010384, which is the electrochemical equivalent of hydrogen. Thus the weight of metal d

e wires from a voltaic cell into it, we shall find the wire from the negative pole become freshly coated with particles of new copper. The sulphate has been broken up, and the liberated metal, being positive, gathers on the negative electrode. Moreover, if we examine the positive electrode we shall find it slightly eaten away, be

nts with a fine degree of accuracy. If, for example, the tubes of the voltameter described on page 38 were graduated, the volume of gas evolved would be a m

king it the cathode in a solution of a salt of gold, and using a plate of gold for the anode. The shops of our jewellers are now bright with

is to be laid, and the double cyanide of silver and potassium when silver is to be deposited. The electrodes are hung from metal rods, the anode A being a plate of gold or silver G, as the case may be, and the cathode C the spoon

n, such as the parts of ordnance, are sometimes copper-plated to preserve them from the action of the atmosphere. Seamless copper pipes for conveying steam

als more subject to corrosion. Nickel is found to deposit best from a solution of the double sulphat

ordan, of London, applied the method to making copies or replicas of medals and woodcuts. Even non-metallic surfaces could be reproduced in copper by taking a cast of them in wax and lining the mould with fine plumbago, whic

oholic solution of nitrate of silver, made by shaking 2 parts of the crystals in 100 parts of alcohol in a stoppered bottle. When dry, the object should be suspended under a glass shade and exposed to a stream of sulphuretted hydrogen gas; or it may be immersed in a solution of 1 part of phosphorus in 15 parts of bisulphide of carbon, 1 part of bees-wax, 1 part of spirits of turpentine, 1 part of asphal

om their ores, in bleaching fibre, in manufacturing hydrogen a