394 



NA TURE 



\_Augusi 24, 1882 



but in this case it would obviously be impossible for it to com- 

 pete in point of economy with the direct combustion of fuel for 

 the attainment of ordinary degrees of heat. Bun en and St. 

 Claire Devil le have taught us, however, that combustion be- 

 cimes extremely sluggish when a temperature of 1,800° C. has 

 been reached, and for effects at temperatures exceeding that 

 limit the electric furnace will probably find advantageous appli- 

 cations. Its specific advantage consists in being apparently 

 unlimited in the degree of heat attainable, thus opening out a 

 new field of investigation to the chemist and metallurgi t. 

 Tungsten has been melted in such a furnace, and 8 pounds of 

 platinum have been reduced from the cold to the liquid condition 

 in 20 minute-. 



The largest and most extensive application of electric energy 

 at the present time is to lighting, but, considering how much of 

 late has been said and written for and against this new illumi- 

 nant, I shall here confine myself to a few general remarks. 

 Joule has shown that if an electric current is passed through a 

 conductor, the whole of the energy lost by the current is con- 

 verted into heat ; or, if the resis'ance be localised, into radiant 

 energy comprising heat, light, and actinic rays. Neither the low 

 heat rays nor the ultra-violet of highe-t refrangibiliiy affect the 

 retina, and may be regarded a- lost energy, the effective rays 

 being those between the red and violet of the spec rum, which 

 in their combination produce the effect of white light. 



Regarding the pi iportion of luminous to non-luminous rays 

 proceeding from an electric arc or incandescent wire, we have a 

 most valuable investigation by Dr. Tyndall, recorded in his 

 work on "Radiant Heat." Dr. Tyndall shows that tie lumi- 

 nous rays from a platinum wire heated to its highest point of 

 incandescence, which may be taken at 1,700° C, formed ,V'> 

 part of the total radiant energy emitted, and T ' 3 th part in the 

 case of an arc light worked by a battery of 50 Grove's element-. 

 In order to apply thc-e valuable data to the case of electric 

 lighting by means of dynam --currents, it is necessary in the first 

 place to determine what is the power of 50 Grove's elements of 

 the size used by Dr. Tyndall, expressed in the practical scale of 

 uni:s as 11 nv established. From a few experiments lately under- 

 taken for myself, it would appear tint 50 such cells have an 

 electro-motive force of o.S'5 Volts, and an internal resistance of 

 13-5 Ohms, giving a current of 7"3 Amperes when the cells are 

 short-circuited. The resistance of a regulator such as Dr. T>n- 

 dall used in his experiments may be taken at 10 Ohms, the 



current produced in the arc would be 



= 4 Am- 



135 + 10+ I 



peres (allowing one Ohm for the leads), and the power con- 

 sumed 10 x 4- = 160 Watts; the light power of such an arc 

 would be about 150 candles, and, comparing this with an 

 arc of 3,308 candles produced by 1,162 Watts, we find that 



V i.e., 7'3 time; the electric energy produce ( " — V i.e., 



160 )' ' J *' v V 150/ 



22 times the amount of light measured horizontally. If there- 

 fore, in Dr. Tyndall's arc ,V" of the radiant energy emitted was 

 visible as light, it follow- that in a powerful arc of 3,300 candles, 



— x —• or fully 1, are luminous rays. In the case of the in- 

 1° ' 7'3 



candescence light (say a Swan light of 20 candle power) we find 

 in practice that nine times as much po ^er has to be expended as 

 in the ca-e of the arc light ; hence j x j = ^ r part of the power 

 is given out as luminous rays, as against ^th in Dr. Tyndall's 

 incandescent platinum — a result sufficiently approximate con- 

 sidering the w ide difference of conditions under which the two 

 are compared. 



These results are not only of obvious practical value, but they 

 seem to establish a fixed relation between current, temperature, 

 and light produced, which may serve as a means to determine 

 temperatures exceeding the melting point of platinum with 

 greater accuracy than has hitherto been possible by actinimetric 

 methods in which the thickne s of the luminous atmosphere nij>t 

 necessarily exerci-e a disturbing influence. It is probably owing 

 to this circumstanct that the temperature of the electric arc as 

 w ell as that of the s dar photosphere has frequently been greatly 

 over-estimated. 



The principal argument in favour of the electric light is fur- 

 nished by its immunity from products of combustion which not 

 only heat the lighted apartments, but substitute carbon c acid 

 and deleterious sulphur compounds for the oxygen upon which 

 respiration depends ; the electric light is white in-tead of yellow, 

 and thus enables us to see pictures, furniture, and flowers as by 

 daylight ; it supports growing plants in tead of poisoning the.n, 



and by its means we can carry on photography and many other 

 industries at night as well as during the day. The objection 

 frequently urged against the electric light, that it depends upon 

 the continuous moti in of steam or gas engines, which are liable 

 to accidental stoppage, has been removed by the introduction 

 into practical use of the secondary battery ; this, although not 

 embodying a new conception, has lately been greatly improved 

 in power and constancy by Plante, Fame, Volckmar, Sellon, 

 and others, and pr maises to accomplish for electricity what the 

 gas-holder has done for the supply of ga^, and the accumulator 

 fur hydraulic transmission of power. 



It can no longer be a matter of reasonable doubt, therefore, 

 that electric lighting will take its place a- a public illuminant, 

 and that even though its cost should be found greater than that 

 of gas, it will be preferred for the lighting of diawing-rooms and 

 dining-rooms, theatres and concert-rooms, museums, churches, 

 warehouses, -how-rooms, printing establishments and factories, 

 and also the cabins and engine-rooms of passenger steamers. In 

 the cheaper and mire powerful form of the arc light, it has 

 proved itself superior to any other illuminant for spreading arti- 

 ficial daylight over the large areas of harbours, railway-stations, 

 and the site, of public works. When placed within a holophote 

 the electric lamp has already become a powerful auxiliary in 

 effecting military operations both by sea and land. 



The electric light may be worked by natural sources of power 

 such as waterfalls, the tidal wave, or the wind, and it is con- 

 ceivable that these may be utilised at con iderable distances by 

 mean- of metallic conductors. Some five years ago I called 

 attention to the vastness of those sources of energy, and the 

 facility offered by electrical conduction in rendering them avail- 

 able for lighting and power supply, while Sir William Thomson 

 made this important matter the subject of his admirable address 

 to section A last year at York, and dealt with it in an exhaustive 

 manner. 



The advantages of the electric light and of the distribution of 

 power by electricity have lately been recognised by the British 

 Government, who have just passed a Bill through Parliament to 

 facilitate the establishment of electrical conductors in towns, 

 subject to certain regulating clauses to protect the interests of 

 the public and of local authorities. Assuming the cost of 

 electric light to be practically the same as gas, the preference 

 for one or other will in each application be decided upon 

 grounds of relative convenience, but I venture to think that 

 gas-lighting will hold its own as the poor man's friend. 



Gas is an institution of the utmost value to the artisan ; it re- 

 quires hardly any attention, is supplied upon regulated terms, 

 and gives with what shiuld be a cheerful light a genial warmth, 

 which often saves the lighting of a fire. The time is moreover 

 not far di-tan', I venture to think, when bith rich and poor will 

 largely resort to gas as the mo t convenient, the cleanest, and 

 the cheapest of heating agents, and when raw coal will be seen 

 only at the colliery or the gasworks. In all cases where the town 

 to be supplied is within say thirty miles of the colliery, the gas- 

 works may with advantage be planted at the mouth, or still 

 better at the bottom of the pit, whereby all haulage of fuel 

 would be avoided, and the gas in its ascent from the battorn of 

 the colliery, would acquire an onward pressu.e sufficient probably 

 to impel it to its destination. The possibility of transporting 

 combustible gas through pipes for such a di-tance has been 

 proved at Pittsburg, where natural gas from the oil district is 

 used in large quantities. 



The quasi monopoly so long enjoyel by gas companies has had 

 the inevitable effict of checking progress. The gas being sup- 

 plied by meter, it has been seemingly to the advantage of the 

 companies to give merely the prescribed illuminating piwer, and 

 to di-cou-age the invention of economical burners, in order that 

 the consumption might reach a maximum. The application of 

 gas for heating purposes has not been encouraged, and is still 

 made difficult in c msequence of the objectionable practice of 

 reducing the pressure in the mains during daytime to the lowest 

 possible point consistent with prevention of atmospheric in- 

 draught. The introduction of the electric light has convinced 

 gas managers and directors that such a policy is no 1 mger ten- 

 able, but must give way to one of technical progress ; new pro- 

 cesses for cheapening the production and increasing the purity 

 and illuminating power of gas are being fully discussed before 

 the Gas Institute ; and improved burners, rivalling the electric 

 light in brilliancy, greet our eyes as we pass along our principal 

 thoroughfares. 



Regarding the importance if the gas supply as it exists at 



