ELECTRIC LIGHTING.

Globe, Volume XXIV, Issue 2640, 22 September 1882, Page 3

ELECTRIC LIGHTING.

The following letter appeared in this morning’s issue of the “ Press ” s Sib, —On looking over what I have before written it may seem that I have been more anxious to point out what may not, than what may be done, Suoh was not my intention when I began j if I knew only of difficulties I would have said nothing. This instalment will, I think, be found of a different nature; but I must travel on the same lines a little longer. , . One of the greatest defects m any system of electric lighting is the large expenditure of energy which has been, till lately, considered necessary to produce a satisfactory result. Not to speak of the voltaic arc, which is the most wasteful of all, I will, to illustrate this, explain the working of a system of incandescent lamps from a “ centre,” that is to say. from the generator itself. Supposing we take a radius of 1000 yards, of which Cathedral square may be the centre. Any plan for the supply of this area would have to include provision for all reasonable expectation of future demand as well as for immediate requirements ; because, if mains, conductors, and machinery were laid down for, say, only fifty consumers, then, if additional requisitions were made, the circuits would have to be all rearranged and different machinery used, or entirely now “ centres," with independent circuits, would be required. This to a certain extent occurs in lighting by gas, but after the laying down of mains the comparison must end. If gas is not wanted for burning it ia not supplied, but the whole electric current necessary to light all the lamps in a circuit most be supplied to that

circuit io long as it is required to make incandescent any of the lamps. Thus, if there were fifty shops in one circuit, and it were required to keep lighted one of them after the lights in the others had been extinguished, then all the power would have to be expended in lighting that single establishment, or even a single lamp in it. Now, in this case whore|does all this power go to F It is dissipated by artificial “ resistances.” The operation necessary to extinguish a light is made to introduce resistance of the same value as that offered by the lamp. If this were not done the motor would “ run away,” the rubbers and the coils of the dynamo would be futed, the lamps still burning would be rendered useless, and, in short, everything left in circuit would be destroyed. lu practice no electrician would allow such a catastrophe to occur, I mention it to show that the moans necessary to prevent it involves an expenditure of energy which, written otherwise, is pure dead loss. In plain figures, an engine of twenty horse-power, a ponderous dynamo, and all the rest of the paraphernalia of an intricate circuit might be required to produce a light of twenty caudle power.

Since the solution of the problem of di viding the electric light this defect has engaged the attention of all, and has been the despair of many electricians. Numerous devices, some tolerably successful, have been used to overcome it. When enterprise pushes itself in our direction we shall, no doubt, hear of “regulators, whereby the turning down of the lights is accompanied by a corresponding saving of motive power in the engine,” of “shunt wound” dynamos, and the like; but the fact will remain that, wherever eleotrio lights are fed direct from the generators great waste and great inconvenience must be result. The inconvenience comes in in this way—A large hotel, for example, manufacturing its own light, the machinery would have to be kept running at times when only a few lights would be required, and dynamos, not taking into account the engines, are not noiseless, far from it. Brush's, Lontin’s, and Da Meritem’ machines, for example, are “ blamed for their load noises, which has been attributed to the resistance of the air, but which are nothing but the sounds due to the alternations of magnetization and demagnetization in the portions of the (Gramme) ring.” The author quoted, Du Moucel, says that these noises are telephouioally repeated in Jabloohkoff candles placed in the circuit of those machines. Noisy machinery would be quite out of place in most situations during the night.

A way hat been found out of most of the difficulties enumerated in this and my former letters, and the accomplishment of domestic and shop electric lighting has been, I think, rendered tolerably easy. It is to be done by the adoption of secondary batteries, or, as they are better known, accumulators, lam not aware that, except for experiment, there is as yet a single secondary battery in use in any of these colonies. lam far from saying that accumulators are all that could be desired, or that they are not being improved day by day; but I do know that at their present development they offer a sure and convenient means of house lighting of far superior quality to, and at least twice as cheaply, as coal gas. The power of them is indisputable. According to Sir Wm. Thompson, one Fours cell (of secondary battery), weighing 1701bs, “ can store and give out again energy to the extent of an hour’s work of one horse power.” At the Crystal Palace Exhibition Messrs Yolckmann and Sellon exhibited a battery of thirty three cells which when fully charged, kept lighted 201 LaneFox lamps, nominally of twenty, but really of nearly thirty candle power each. These cells are claimed to be able to store for one hour’s work five horse-power, or one horse-power for five hours’ work, and so on, “ The sparks given off on connecting several cells of the folly charged battery are remarkably violent, the deflagrated wire flying off in a perfect shower of red hot sparks of copper, accompanied by loud cracks. Gn examining the wire afterwards it was found to be literally torn asunder in small pieces by the force of the discharge.” These cells weighed each SSOibs. As a pendant to the above I may mention that at a recent meeting of the British Association, Mr Swan produced a " portable electric lamp of two candle power, which could be kept lighted for six hours by a two cell accumulator, weighing lOlbs." The range of power indicated by these examples is thus seen to be ample for all purposes. At present the cells ere somewhat oumbrons, so far as weight goes, and I do not look for much improvement in them in this direction, but they pack closely, a good size being about as large as a brandy case. One of each pair of the elements [or plates in them will, when in nse, last almost indefinitely, while the other will only require renewal once in, say, fifteen months, as far as can at present be seen. When properly applied their functions should in electric lighting be : exactly similar to those of gasometers in the gas-lighting system. Their weight, as I have said, Is a .ainst them, but there is nothing to prevent a shopkeeper having bis light source stowed away under bis counter, or elsewhere, in as small a space. They are not to be “ carted about,” as 1 have somewhere seen mentioned, nor is it required that they should be. For lighting a town it would be necessary to have one or more depots. From these places mains containing -two wires only would run through every street. Premises to be lighted would have deposited a sufficient number of accumulator cells to supply the light required. The cells would be connected with the main cables by service wires, and so charged in the daytime. When fully charged each tenement would be cut off from the main cable until the next day, when the same process would be gone through again. The result would be that each customer would be independent of the reet, and no tampering at points oonld injure the system as a whole. The saving would be manifold. There would not be a network of wires to maintain, and there would not be the diasipation of force in artificial resistanoes. The maohinery would be many times smaller than that required for any system of direct lighting, and lastly, every unit of force generated would be profitably used, for when joined in circuit each morning the force imprisoned in the cells would equalise itself throughout the whole, and no more would require to be supplied from the depot than would be sufficient to replace the aggregate consumption of the I previous night. As for the lighting of the | streets the scheme would leave the cable free for their supply at night, and they should be supplied from batteries of very largo size stationed at different parts] of the town, the batteries to be charged by night or day as might suit the trade. For the information of my scientific friends I add that I have not lost sight of the fact that inoandeso nt lamps, as well as arc lights, are best served by alternate current dynamos, while secondary batteries most bo charged from continuous current machines. For the general reader I may say that the carbons of a light, whether of the voltaic arc or incandescent, if made to receive their supply from the fixed poles of a generator wear away unequally, the positive is consumed about twice as fast as tne negative. Moat machines are now made to change the poles of the current with great rapidity, and so equalise the oombustion of the carbons. Sooner than abandon the accumulator, X would bo prepared to submit to the irregularity of consumption of carbons, but, I think, the defect can be remedied by a very simple contrivance, so far as is necessary in practice. The cost of the scheme thus outlined can be easily calculated. Whether or not it, or any other schema, should bo taken np by the City Council, or whether that body should sell a “ concession ” to a company, and so lay the foundation of a monopoly similar to that now enjoyed by the Gas Company, is foreign to my purpose to enquire, but it is certain that the City Council could do the work better and cheaper than eny oompiny whatever.

In conclusion, I say, and I have no fear but my propositions will, by experience, be found to be sound:—(l) The arc light has had its trial, and, except for special purposes, has been found to be a failure. (2) Lighting direct from a dynamo is much more expensive, troublesome, and uncertain than from accumulators. (3) Lighting can be meat cheaply done in private establishments where the outlay for gas warrants the expenditure on independent plant; and (4) Electric lighting to servo streets, shops, and dwellings can be supplied on some such plan as I have indicated at very much less than the cost of gas. Tours, &c., Geo. Bibd. Christchurch, September, 15th, 1882,

P.B.—la this and former letters I have availed myself of many valtiablo_ suggestions by a gentleman of large experience, whose name, if necessary, will be forthcoming.— Q-. 8,