Sept. 7, 1888.] 



SCIENTIFIC NEWS. 



247 



One candle light maintained by tallow 



wax 



watts 

 absorbs 124. 



,. 94 



86 



80 



57 

 68 



.„ ,, sperm „ 



,, „ mineral oil ,, 



„ ,, vegetable oil „ 



„ „ coal gas „ 



,, ,, cannel g?s „ 48 



„ ,, electricity (glow) „ . 3 



,, ,, electricity (arc) ,, 55 



The relative heat generation of these illuminants may be estimated 

 from these figures. 



Though the electric light was discovered by Davy in 1 810, it was 

 not until 1844 that it was introduced into our scientific laboratories by 

 Foucault ; it was not until 1878 that Jablochkoff and Brush showed 

 how to light up our streets effectually and practically ; it was not 

 until 1 88 1 that Edison and Swan showed how our homes could be 

 illuminated softly and perfectly. 



The greatest development of the electric light has taken place on 

 board ship. Our Admiralty have been foremost in this work. All 

 our warships are gradually receiving their equipment. Our ocean- 

 going passenger ships are also now so illumined, and perhaps it is 

 here that the comfort, security, and true blessedness of the electric 

 light is experienced. 



Railway trains are also being rapidly fitted up. The express 

 trains to Brighton have for a long time been so lighted, and now 

 several northern railways, notably the Midland, are following suit. 

 Our rocky coasts and prominent landfalls are also having their 

 lighthouses fitted with brilliant arc lamps, the last being St. 

 Katherine's Point on the Isle of Wight, where 60,000 candles throw 

 their bright beams over the English Channel, causing many an 

 anxious mariner to proceed on his way rejoicing. 



Fontaine showed in Vienna, in 1873, tnat a dynamo was re- 

 versible — that is, if rotated by the energy of a moving machine, it 

 would produce electric currents ; or, if rotated by electric currents, 

 it would move machinery. An electric current is one form of 

 energy. If we have at one place the energy of falling water, we 

 can, by means of a turbine and a dynamo, convert a certain portion 

 of the energy of this falling water into an electric current. We 

 transmit this current through proper conductors to any other place 

 we like, and we can again, by means of a motor, convert the energy 

 of the current into mechanical energy to do work by moving 

 machinery, drawing tramcars, or in any other way. We can in this 

 way transmit and utilise 50 per cent, of the energy of the falling 

 water wherever we like. The waste forces of nature are thus within 

 our reach. The waterfalls of Wales may be utilised in London ; 

 the torrents of the Highlands may work the tramways of Edinburgh ; 

 the wasted horse-power of Niagara may light up New York. The 

 falls of Bushmills actually do work the tramway from Portrush to 

 the Giant's Causeway, and those of Bessbrook the line from Newry 

 to Bessbrook. 



The practicability of the transmission of energy by currents is 

 assured, and the economy of doing this is a mere matter of calcula- 

 tion. It is a question of the relative cost of the transmission of fuel 

 in bulk, or of the transmission of energy by wire. Coal can be 

 delivered in London for 12s. per ton. The mere cost of the up- 

 keep of a wire between Wales and London to deliver the same 

 amount of energy would exceed this sum tenfold. For long dis- 

 tances the transmission of energy is at present out of the question 

 There can be no doubt, however, that for many purposes within 

 limited areas the transmission of energy by electricity would be 

 very economical and effective. Pumps are worked in the mines of 

 the Forest of Dean, cranes are moved in the works of Easton and 

 Anderson at Erith, lifts are raised in banks in London ; water is 

 pumped up from wells to cisterns in the house of Sir Francis Trus- 

 cott, near East Grinstead ; ventilation is effected and temperature 

 lowered in collieries ; goods, minerals, and fuel can be transmitted 

 by telpherage. 



The transmission of power by electricity is thus within the range 

 of practice. It can be distributed during the day by the same 

 mains which supply currents for light by night. Small industries, 

 such as printing, watch-making, tailoring, boot-making, can be 

 cheaply supplied with power. It is thus brought into direct com- 

 petition with the distribution of power by steam as in America, or 

 by air-pressure as in Paris, or by high-pressure water as in London ; 

 and the relative advantages and economies of each system are 

 simple questions of calculation. When that evil day arrives that 

 our supply of natural fuel ceases, then we may look to electricity 

 to bring to our aid the waste energies of nature — the heat of the 

 sun, the tidal wave of the ocean, the flowing river, the roaring falls, 

 and the raging storm. 



The property, which the electric current possesses, of doing work 

 upon the chemical constitution of bodies so as to break up certain 



liquid compounds into their constituent parts, and marshal these 

 disunited molecules in regular order according to a definite law 

 upon the surfaces of metals in contact with the liquid where the 

 current enters and exists, has led to immense industries in electro- 

 metallurgy and electro-plating. The extent of this industry may 

 be gathered from the fact that there are 172 electro- platers in 

 Sheffield and 99 in Birmingham. The term electro-metallurgy was 

 originally applied to the electro-deposition of a thin layer of one 

 metal on another ; but this is now known as electro-plating. 



In 1839 Jacobi in St. Petersburg and Spencer in Liverpool laid 

 the foundations of all we know of these interesting arts. Copper 

 was deposited by them so as to obtain exact reproductions of coins, 

 medals, and eDgraved plates. The first patents in this country and 

 in France were taken out by Messrs. Elkington, of Birmingham, 

 who still occupy the foremost position in the country. 



The fine metals, gold and silver, are deposited in thin layers on 

 coarser metals, such as German silver, in immense quantities. 

 Christofle of Paris deposits annually six tons of silver upon articles 

 of use and of art, and if the surfaces so electro- plated were spread 

 out continuously they would cover 140 acres. 



The whole of the copper plates used in Southampton for the 

 production of our splendid Ordnance survey maps are deposited by 

 copper on matrices taken from the original engraved plates, which 

 are thus never injured or worn, are always ready for addition or cor- 

 rection, while the copies may be multiplied at pleasure and renewed 

 at will. 



Nickel-plating, by which the readily oxidisable metals like iron 

 are coated with a thin layer of the more durable material nickel, is 

 becoming a great industry ; the trappings of harness, the exposed 

 parts of machinery, the fittings of cycles and carriages and in- 

 numerable articles of daily use are being rendered not only more 

 durable but more beautiful. 



The electro-deposition of iron, as devised by Jacobi and Klein, 

 in the hands of Prof. Roberts- Austen, F. R.S., is giving very in- 

 teresting results. The dies for the coins which were struck at our 

 Mint on the occasion of the Jubilee of the Queen, were modelled in 

 plaster, reproduced in intaglio by the electro deposition of copper, 

 and on these copper moulds hard excellent iron in layers of nearly 

 l-ioth of an inch was deposited. 



The extraction of metals from their ores by deposition has re- 

 ceived wide application in the case of copper. In 1871 Elkington 

 proposed to precipitate copper electrolytically from the fused sul- 

 phide of copper and iron known to the copper smelter as "regulus." 

 Thin copper plates were arranged to receive the deposited copper 

 while the foreign metals, including gold and silver, fell to the 

 bottom of the solution, the process being specially applicable, it 

 was supposed, to regulus containing small quantities of the precious 

 metals. 



The electrical purification of copper from impure ' ' blister 

 copper" or "blade copper" has also made great progress, and 

 special dynamos are now made which will, with an expenditure of 

 100 horse-power, precipitate 18 tons of copper per week. The 

 impure metal is made to form the anode in a bath of sulphate of 

 copper, the metal being deposited in the pure form on a thin copper 

 cathode. 



Both at Swansea and Widnes immense quantities of copper, in 

 spite of the restrictive operations of the copper syndicate, are being 

 produced by electro-deposition. Copper steam pipes for boilers 

 are now being built up of great firmness, fine texture, and con- 

 siderable strength by Mr. Elmore at Cockermouth, by electro- 

 deposition on a rotating mandril in a tank of sulphate of copper. 

 By this process one ton of copper requires only a little more than 

 one ton of coal to raise the requisite steam to complete the opera- 

 tion. 



It has been shown that the electrolytic separation of silver from 

 gold by similar methods is perfectly practicable. The value of the 

 material to be dealt with may be gathered from the fact, communi- 

 cated to the "Gold and Silver Commission" now sitting, that 

 nearly 90,000,000 ounces of silver are annually produced, and the 

 greater portion of this amount contains sufficient gold to render 

 refining remunerative. Although the old acid process of " part- 

 ing " gold and silver remains practically undisturbed, there seems 

 no reason to doubt that in the future electricity will render us good 

 service in this direction as it has already in the purification of 

 copper. 



There is not much actual progress to report in the extraction 

 of gold from its ores by electrical agency. The conversion of 

 gold into chloride of gold by the direct, or indirect, action of chlorine 

 is employed on a very large scale in [Grass Valley] California and 

 elsewhere. This fact has led to well-directed efforts to obtain by 

 electrolytic action, chlorine which should attack finely divided gold 

 suspended (with the crushed ore) in the solution from which the 

 chlorine was generated, the gold, so converted into soluble 



