Unlike Mr Edison, Mr Werdermann does not believe in the indefinite divisibility of the electric light. It will be observed that the candle power of the light becomes diminished by subdivision. Two lights gave a light equal to 700 candles, whereas the same current divided into ten lights gave an aggregate light of only 400 candles.
The following extract from the ‘Times’ of December 5th, 1878, illustrates the financial aspect of the electric light question:—
“At the usual weekly meeting of the Society of Arts, held last evening, Dr C. W. Siemens, F.R.S., in the chair, a paper on electric lighting was read by Mr J. N. Shoolbred, M. Inst. C.E. The object of the author was to present some results of the application of electric lighting to industrial purposes, especially as
regards cost. He noticed first the Holmes and the Alliance magneto-electric machines, giving alternating currents and single lights for lighthouse use. Secondly, he referred to the dynamo-electric machines, producing single lights for general industrial purposes, as well as for lighthouses, and including the Siemens and the Gramme machines. In his third group the author included the machines used for producing divided lights, each group indicating a marked period representing a clearly defined stage of progress in electric lighting. With regard to cost, Mr Shoolbred stated that in every instance his figures and particulars were those afforded by the users of the various lights, and not by the inventors or their representatives. In the case of the Holmes machine the annual cost per lighthouse was about £1035, inclusive of interest, repairs, and wages. With the Siemens machine the annual cost was about £494 per lighthouse, including interest and the other expenses. With the Alliance machine as used at Havre the cost was about £474 per annum per lighthouse, interest, &c., included. The single-light Gramme machine has been in use in the Paris goods station of the Northern of France Railway for two years. Six machines have been kept going with one light each, and the cost is found to be 5d. per light per hour, or with interest on outlay at 10 per cent., 8d. per hour. The same light at the ironworks of Messrs Powell at Rouen was stated to cost 4d. per light per hour, exclusive of interest and charge for motive power, the latter being derived from one of the engines on the works. In 1877 a series of experiments were carried out with the Lontin light at the Paris terminus of the Paris, Lyons, and Mediterranean Railway. The passenger station was lighted, and the results were so satisfactory that the company have entered into a permanent contract with the proprietors of the Lontin light for lighting their Paris goods station with 12 lights, at a cost of 5d. per light per hour. The Western of France Railway Company have had 6 Lontin lights in the goods station at the Paris terminus, St Lazare, since May last, and 12 lights in the passenger station since June. Careful experiments have shown the cost to be 8d. per light per hour, inclusive of interest. Referring to the Jablochkoff light, Mr Shoolbred placed before the meeting some particulars with regard to its application in the Avenue de l’Opéra, Paris, which were afforded him by M. J. Allard, the chief engineer of the lighting department of the City of Paris. It appears that the authorities pay the Société Générale d’Électricité 37f. 2c. per hour for the 62 lamps in use there. These 62 lamps supersede 344 gas-jets which were previously used, and which cost the authorities 7·244f. per hour. The electric illumination, however, is considered as equal to 682 gas-jets, or about double the original illumination—that is, to a cost of 14·45f. per hour as
against 37·2f. for the electric light, the cost of which, therefore, is 2·6 times that of the gas. The contract for lighting by electricity was terminated by the City of Paris on the 30th ult., and the authorities have declined to renew it except at the price paid for gas, namely, 7·224f. (or about 6s.) per hour, and that only until the 15th of January next. These terms have been accepted by the Société, so that the price paid to them will be at the rate of about 11⁄8d. per light per hour. Mr Shoolbred stated that the Société place their expenses at 1·06f. (or just 11d.) per light per hour, which, however, they hope shortly to reduce by one half. A series of careful photometric experiments carried out by the municipal authorities with the Jablochkoff lights, above referred to, showed each naked light to possess a maximum of 300 candles of intensity. With the glass globe this was reduced to 180 candles, showing a loss of 40 per cent., while during the darker periods through which the lights passed the light was as low as 90 candles. The foregoing were the only authenticated particulars which the author could obtain as regards the working of the various electric systems of electric lighting. In conclusion, Mr Shoolbred referred to the Rapieff light at the ‘Times’ office, which, he observed, worked fairly and with regularity, which could not be said of all others, and it might therefore be entitled to take rank as an established application of electric illumination. The paper was illustrated by the Siemens, Rapieff, Serrin, and other forms of electric light, which were shown in operation.”
That the electric light is eventually destined to supplant coal gas in illuminating the fronts of large buildings, open spaces, squares, assembly rooms, public halls, theatres, picture galleries, workshops and factories, &c., seems no very extravagant prediction. We have already seen that it has for some years been employed in one lighthouse; and we have the testimony of Mr Douglas, of the Trinity House, at a very recent meeting of the Society of Arts, that at the Souter Point Lighthouse there had been only two stoppages in eight years, once through a bad carbon breaking, and once through the lighthouse-keeper going to sleep.
In addition to places above specified, amongst other localities in which it is in work, we may mention the chocolate factories of M. Menier, at Noiselle, his india-rubber works at Grenelle, his sugar refinery at Nice, and Messrs Caille’s works at Paris. In this country it was employed in the erection of the Tay Bridge, as well as in the works of Messrs Head, at Stockton-on-Tees, and in London it may be nightly seen burning before the Gaiety Theatre in the Strand, at Billingsgate Market, and frequently lighting up the front of the Stereoscopic Company’s premises in Regent Street. Further, we may add that the Metropolitan Board of Works are making
the experiment of lighting the Victoria Embankment and the City authorities the Holborn Viaduct, with the Jablochkoff candle. The former have placed a dynamo-electric apparatus, worked by a steam engine of 20-horse power, close to the foot of Hungerford Bridge, from whence wires will be carried right and left towards Westminster and Blackfriars respectively.
We believe the main conducting wire is carried under the coping-stone of the parapet running along the Embankment, and that the carbon points are fixed on the top of a certain number of gas standards which now surmount the wall of the Embankment.
That electricity is more economical as a method of artificial lighting than coal-gas the figures previously given seem to demonstrate, and there can be no question as to the much greater luminosity and purity of the light over the gas flame, qualities which render it an admirable substitute for the sunlight, the absence of which it may be said to supply at night. One disadvantage urged against its employment in weaving rooms is, that it casts such dark and distinct shadows that these are frequently mistaken for the threads themselves, an objection which is said to have been remedied by placing the light as near the ceiling as possible. The non-generation of carbonic acid and sulphurous products such as are given off by burning gas, although of slight importance when the light is employed in the open air, becomes a great advantage when it is used in crowded assembly rooms or theatres, since the atmospheric contamination caused by carbonic acid becomes of course considerably reduced. The absence of sulphur compounds especially qualifies the light for use in large libraries. If it be true that the light gives rise to an appreciable amount of ozone, this constitutes another point in its favour. Opinion is at variance as to the possibility of the practical application of the electric light for illuminating private houses and dwellings in such a manner as to supply the place of the gas we now burn in them. One serious impediment to the probable accomplishment of this result certainly seems to be the fact that electricity for lighting purposes can only practically be conveyed to short distances from its source, which would necessitate the establishment and supervision of a number of generating machines near the houses to be lighted. Another obstacle, which hitherto has not been overcome, is the circumstance that the current when subdivided yields proportionately a greatly diminished amount of light. For instance, one light which had a certain photometric candle valve would yield when divided into two an aggregate amount of light considerably less than the one; and if divided into three still less, and so on. This has been pointed out when noticing Mr Werdermann’s invention for the divisibility of the light. Mr Edison, an American inventor,