Lighting
Lighting.—The illumination of a dwelling is a most important consideration, as regards comfort and health.
Daylight.—Natural lighting is provided for by windows. The window area of a room should be well proportioned. In dwelling-rooms, it may amount to half the area of the external wall containing the windows; in churches, &c., ⅓ will suffice. Too great a window area is objectionable, as it considerably lowers the interior temperature in winter, unless very thick glass and double windows are provided. When windows become steamed or covered with condensed moisture in frosty weather, this can be cured by applying a very thin coat of glycerine on both sides of the glass. When direct daylight cannot be got, great advantage may be derived from using polished metallic reflectors.
Luminous Paints.—Several bodies possess the property of absorbing a certain amount of light and emitting it slowly. The most important of these is calcium sulphide. This property has been utilised by mixing the mineral with paint as a covering for surfaces where the light is required. The illumination, however, is very feeble.
Candles.—Candles will long retain a place in domestic lighting from their safety and convenience for carrying about. At the same time they are an expensive source of light, and not very powerful. It may here be mentioned that there is a right and a wrong way of blowing out a candle. If the candle is held on a level with the blower’s mouth, or blown down upon, as usual, as it stands on a shelf or table, the wick will smoulder and smoke till the room is filled with its disagreeable smell, and the wick burned away so that it can be lit next time with difficulty. If the candlestick is held well above the blower’s head, and the flame blown out from below, the ignited wick will almost immediately be extinguished, and no trouble will be found in re-lighting the candle. Avoid cheap candles; they burn rapidly to waste and play havoc with clothes and furniture by “dropping.” The best form of candlestick yet introduced is the “silver torch,” made by Wm. Nunn & Co., 204 St. George Street, London, E. By this the candle is converted into a lamp, with or without a globe as desired; the candle is completely consumed, leaving no ends, and guttering and dropping are quite prevented. Nightlights should always be burned under a glass shade, such as Clarke’s.
Oil Lamps.—All lamps intended for burning animal, vegetable, or mineral oils as illuminants should have the following objects in view:—To supply oil regularly to the wick; to apportion the supply of air to the description and quantity of oil to be burnt; to provide simple means for regulating the height of the wick, and consequently, the flame; and finally, to place the burning portion of the lamp in such a position as not to be obscured by the reservoir and other portions. The oldest lamps, as the antique Etruscan, and the cruisie of Scotland, were on the suction principle, and the wick depended for its supply upon its own capillary action. As the level of the oil was constantly varying, so the light varied also, and the first attempts of inventors were directed to maintaining an equal level of oil. The bird-fountain and hydrostatic reservoirs partly attained this end, and the Carcel and Moderator systems were perfect of their class, mechanical or pressure lamps. It is evident that suction lamps depend for their efficacy upon the gravity of the combustible. A spirit lamp, with a good wick, will burn very well, though the wick be several inches above the liquid. With liquids volatilising at low temperatures, there is always a danger of the formation of explosive mixtures.
In the Silber lamp the burner is a simple aggregation of concentric tubes. The use of these, especially of the innermost, bell-mouthed pipes, becomes very apparent in the lighted lamp. Remove the interior tube, and immediately the flame lengthens and darkens, wavers and smokes. The current of air which is, by this internal conduit, directed into the interior flame surface, is the essential principle of Silber’s invention. The wick is contained in a metal case, surrounded by an air-jacket, which passes down the entire length of the lamp, leaving a small aperture at the base, through which the oil flows from the outer reservoir to the wick chamber. Thus, by the interposition of an atmospheric medium, the bulk of the oil is maintained throughout at a low temperature; 2 concentric bell-mouthed tubes pass down the interior of the wick case, and communicate with the air at the base of the lamp, which is perforated for the purpose; 2 cones, perforated, the inner and smaller throughout, the largest only at the base, surround the wick, and heat the air in its passage through the holes to the flame. The effect of these appliances is, firstly, by the insulation of the outer reservoir, to avoid all danger of vaporisation of the oil, till actually in contact with the wick. As it is drawn nearer and nearer the seat of combustion, the hot metal wick-holder heats, and ultimately vaporises the luminant, so that at the opening of the wick tube concentrically with the air conduits—all of which are exceedingly hot—a perfect mixture of vapour and hot air is formed, and burned. An all-important feature is the shape and position of the chimney, which influences the flame to the extent of quadrupling its brilliancy if properly adjusted. (Field, Cantor Lecture.)
48. Hinks’s Safety Lamp.
The many fires and fatal accidents arising from explosions of mineral oil lamps has drawn official attention to the subject of rendering them safe. Sir F. Abel has stated that all channels of communication between the burner and the reservoir of mineral oil lamps should be protected on the principle of the miners’ safety lamp; he added that a simple arrangement which effected the desired object “with perfect safety” was to attach to the bottom of the burner a cylinder of wire gauze of the requisite fineness, which prevented the transmission of fire from the lamp flame to the air-space of the reservoir. Acting upon this suggestion, Hinks and Son, 60 Holborn Viaduct, have introduced a wire-gauze cylinder for use with their duplex lamps, which renders them absolutely safe. Another advantage with their lamps is the ease with which they are lit and extinguished, as shown in Fig. 48: for lighting, a turn of the thumb-key a gently raises the cone, globe, and chimney, giving free access to the wicks; to extinguish them, it is only necessary to press the lever b.
The Defries safety lamp (Defries Safety Lamp and Oil Co., 43 Holborn Viaduct) is attracting much notice, on account of economy, safety, and illuminating power. The construction of the lamp is such that neither ignition of the vapour, nor outflow of the oil in the event of the lamp being overturned, can occur. Moreover, the oil reservoir, being of metal, is not liable to fracture. It therefore follows that the risks attaching to the employment of mineral oils as illuminating agents in lamps of the ordinary description are non-existent in this lamp. The light emitted is remarkably white, the flame is perfectly steady, and the combustion is effected without the production of the slightest odour or smoke. Results of photometric tests by Prof. Boverton Redwood were more favourable than any he had hitherto obtained with mineral oil lamps of other forms. The illuminating power is, for the size of the burner, in each case very high, while the consumption of oil per candle light per hour is remarkably small. The products of combustion are odourless, even when the normal size of the flame is much reduced by lowering the wick. Any mineral oil, as well as the Defries safety oil, can be used in these lamps. This is quite odourless when spilled or heated, requires a temperature of 308° F. (or 96° F. above the boiling point of water) for its ignition, and does not vaporise below 270° F. Such oil is no more inflammable than colza oil, and is moreover free from the risk of spontaneous combustion. Its price is 1s. 6d. per gal. The absolute necessity for using, in any and every lamp, the most refined and safest grades of mineral oil cannot be too seriously insisted upon, Cheap low oils mean personal risk.
Gas.—Though gas is long since established as one of the most successful and general illuminants, it is surprising what ignorance exists as to the simple rules which should govern its use.
This section is not intended for the guidance of the professional gasfitter, yet some of the points to be noticed are really within his province, and are mentioned because the householder should be in possession of such knowledge as will enable him to discover or prevent faulty work.
Coal gas, being much lighter than air, flows with greatest velocity in the upper floors of houses; hence the supply pipe may diminish in size as it rises, say from 1¼ in. at the basement to ¾ in. on the 3rd floor. At a point near the commencement of the supply pipe it should be provided with a “siphon,” which is simply a short length of pipe joined at right angles in a perpendicular position and closed at the lower end by a plug screwed in. As all gas-tubes should be fixed with a small rise, this siphon will collect the condensed liquids, which may be drawn off occasionally by unscrewing the plug end. When the lights flicker, it shows there is water in the pipes: the siphon prevents this. The number of gas-burners requisite for lighting a church or other large building may be computed thus. Take the area of the floor in ft. and divide by 40, will give the number of fish-tail burners to be distributed according to circumstances. Example: a church 120 ft. long by 60 ft. wide, contains 7200 ft. area; divided by 40, gives 180 burners required for the same. Burning gas without a ventilator or pipe to carry off the effluvia, is as barbarous as making a fire in a room without a chimney to carry off the smoke. If a pipe of 2 in. diameter were fixed between the joists, with a funnel elbow over the gaselier, and the other end carried into the chimney, it would be a general ventilator. Of course, an open ornamental rosette covers the mouth of the tube; or an Arnott valve ventilator over the mantelpiece would answer the same purpose. In turning off the gas-lights at night, it is usual, first, to turn off all the lights, except one, and then turn off the meter main cock, and allow the one light to burn itself out, and then turn it off. The evil of this system is this,—by allowing the one light to burn itself out, you exhaust the pipes and make a vacuum, and of course the atmospheric air will rush in. The proper way is to turn off all lights first, and finally the meter, thus leaving the pipes full of gas and ready for re-lighting. These few remarks have been derived from Eldridge’s ‘Gas-Fitter’s Guide,’ an eminently useful and practical handbook.
It was formerly the practice to make all gas-burners of metal; the openings, whether slits or holes, from which the gas issued to be burned being small, in order to check the rate of flow. This was an error, for heat and light go together, and the metal, being a good conductor of heat, kept the lower part of the flame cold. The part of burners actually in contact with the flame is now invariably of some non-conducting material, such as steatite; and the effect of this simple improvement is most noteworthy. Bad burners show a great proportion of blue at the lower part of the flame, and the upper or luminous portion is small and irregular in shape, and dull in colour. These effects are due to gas issuing at too great velocity from small holes in burners, as well as to improper material in the latter. The illuminating power of coal gas depends upon the incandescence, at the greatest possible heat, of infinitesimal particles of carbon which it contains, invisible until heated. In the lower, or blue portion of the flame, the heat is not sufficient to render these particles incandescent; and it is necessary that this effect should be secured at the nearest point to the burner. Unless this is done, the light is not only lessened, but the unconsumed carbon passes off and is deposited as soot on ceilings and furniture. Blackened ceilings are a measure of the badness of the burners. It will now be seen why a material which cools the flame should not be used for a burner, for the hotter the flame, the more perfect is the incandescence of the carbon for which in reality the consumer pays, and the less danger there is of blackened ceilings. But in addition to the better material, the construction of even the cheapest modern burners is very greatly improved; although even a good burner may be subjected to such conditions—e.g. allowing gas to be driven through it at a high velocity, a condition usually accompanied by a hissing or roaring sound—as to give a bad result. The capacity of burners should moreover bear a reasonable proportion to the quality of the gas for which they are required to be used. Thus with rich Scotch gas, burners with very small holes, consuming only about 1½ cub. ft. hourly, are sometimes adopted for economical reasons. Occasionally these burners find their way South, but their use for the ordinary qualities of English gas is the worst possible economy. It is difficult to lay down hard and fast rules for the sizes of burners, the purposes for which gas-light is required being so various. For an ordinary apartment, however, wherein distributed lights are adopted, 5 ft. burners with 14 or 15 candle gas, 4 ft. burners with 16 or 17 candle gas, 3 or 3½ ft. burners with 18 or 20 candle gas, and 2½ ft. burners with richer gas will be found to give satisfactory results. It may be remarked that these figures apply to burners regulated in some way to the given rates of consumption, and not to those merely reputed to be of the stated sizes. Various means are adopted for checking the flow of gas, not at the point of ignition, but at some prior point of its course; because it has been found that the slower the rate of flow at the commencement of combustion, the better the result obtained.
Clustering of gas-lights is bad. All parts of a room should be as nearly as possible equally lighted, the only noteworthy exception to this rule being in the case of a dining-room, where concentration of light upon the table is not only permissible but is even demanded. Hence in most cases wall brackets give the best effect, and such masses of light as are afforded by pendants of many arms are to be avoided, or are only required in very large rooms where portions of the floor area would otherwise be insufficiently lighted. When it is desired to light a drawing-room with wax candles—than which nothing is more beautiful—they are distributed wherever support can be found for them. As every gas flame may be considered equal to 12 or 15 candles, with all their wicks together, the inadvisability of further concentration is evident. In fact, gas is if anything too brilliant for living-rooms, and if it were always properly distributed, many a dimly-lighted apartment would be perfectly illumined with the same number of burners which, when massed, appear insufficient. Where concentrated ceiling lights are needed for dining-rooms, many-armed pendants are seldom satisfactory, owing to the shadows which most of them cast. In these cases a single powerful argand light in a suitable reflecting pendant, or a cluster of flat flames similarly provided, will give a better result than the usual branched chandelier, and with a material saving in gas. For it is a curious and valuable property of gas, that large burners can be rendered much more economical in proportion than smaller ones. Thus, if the 4 burners of a branched chandelier give altogether the light of (say) 50 candles, the same illuminating power may be obtained from a greatly reduced quantity of gas when concentrated in a single burner of the most improved kind.
With regard to the smaller flat flames, which are the most general for ordinary lighting, the selection of glass globes is a very important matter. It may be said at once that all the old-fashioned style of glasses, with holes in the bottom about 2½ in. diam., for fitting into the brass galleries of the older pattern pendants and brackets, are objectionable. The reasons for this condemnation are few and simple. It seems never to have occurred to the makers of these things that the gas flames inside the globes are always wider than the openings beneath them, through which the air required for combustion passes; and that, as a rule, the light of the flame is required to be cast downward. Gas flames always flicker in these old-fashioned glasses, because the sharp current of entering air blows them about. And the light cannot come downward because of the metal ring and its arms, and the glass, which is always thicker and generally dingier at this part of the globe. Perfectly plain and clean glass absorbs at least 1/10 of the light that passes through it; ground glass absorbs ⅓; and the ordinary opal obstructs at least ½, and generally more. Only those globes should be chosen therefore which have a very large opening at the bottom, at least 4 in. wide, through which the air can pass without disturbing the flame. The glass then fulfils its proper duty, screening the flame from side draughts, and not causing mischief by a perpetual up-current of its own. Good opal or figured globes of this pattern may be used without disadvantage, because the light is reflected down through the bottom opening more brightly than if there were no globe, while the flame is shaded and the light diffused over other parts of the room.
The degree to which the luminosity of gas is utilised depends very largely upon the burner, people too often setting down as the fault of the gas, defects which should really be ascribed to the burner. In 1871, the Commission appointed by the Board of Trade to watch over the London gas supply, and whose prescriptions in these matters are more or less recognised by the whole country, made an examination of a collection of gas-burners from a large number of sources, and including those in general use. The greater portion of these gave only ½, some even only ¼ of the light that the gas was actually capable of affording. Two points very often neglected are: (1) that the size of the burner should be proportionate to the quantity of gas required to be consumed by it, and (2) that the gas should issue at a very low velocity. In good argands, the pressure at the point of ignition is almost nil; and in flat-flame burners, the pressure should be only just sufficient to blow the flame out into the form of a fan. It is also very necessary that the body of the chamber below the point of ignition should be of material with low heat-conducting power, so that the gas may undergo no increase in volume which would occasion a proportionate increase of velocity, and that the heat may not be conducted away from the flame. To establish this, Evans had 2 argand burners made, differing only in that one had the combustion chamber of brass, and the other of steatite. The latter gave more light than the former in the proportion of 15 to 13 for the same quantity of gas. As another example a No. 8 metal flat-flame burner, consuming 5 cub. ft. of gas per hour, gave a light equal to 11·5 candles, while a steatite burner of corresponding size, with non-conducting combustion chamber, gave 14·6 candles. Another metal burner of a description somewhat generally used, gave about ⅜ of the light that the gas was capable of yielding. Worn-out metal burners generally give the best results, as the velocity of the issuing gas is lower than when the burners are new. A much better result is obtained by burning, say 20 cub. ft. of gas from one burner, than by using 5 burners, each of which consumes 4 cub. ft. This is the reason why the modern argands give so much more light than the older ones, which were drilled with a very large number of holes, and were more suitable for boiling water than for illuminating. If the air which is to support the combustion be heated before it reaches the flame, especially in the case of flat-flame burners, better results are produced, as was pointed out by Prof. Frankland more than 10 years ago, and this principle is now being carried out by some Continental burner makers. Of modern argands there are many excellent varieties, which can evolve 15-30 per cent. more light for the same quantity of gas than the best flat-flame burners. One kind consisting of 3 concentric rings of flame with steatite gas chambers was first used in the public lighting of Waterloo Road in 1879. In another the products of combustion are brought down in a flue fastened round the burner, so as to heat the air which supports the combustion as it passes in pipes through the flue above mentioned to the flame; while a third kind has an arrangement for admitting separate currents of cold air to keep the chimney cool. There seems little doubt that the argand lamp will play a leading part in the gas lighting of the future. An important point connected with the use of gas is that the heat generated by combustion, may be made to do the work of ventilation, as in the fish-gill ventilator invented by the late Goldsworthy Gurney. In this strips of calico are nailed, by the two upper corners, across an opening in the wall, in such a way that each strip laps over the strip next below it. This contrivance, opening and closing like the gills of a fish, is self-acting, as the heated air passes away through the porous material, and cold air is admitted without draught.
Gas is often accused of heating the rooms; but if persons, when burning candles would increase the number of the candles so as to equal the light of the gas-flame, the heat given out would be found to be less when burning gas than when burning lamps or candles.
49. Stott’s Governor.
It is very beneficial to regulate the pressure at which gas reaches the burners, and many complaints of impurity of the air of a room, caused by gas, arise from this want of regulation of pressure. It can be attained by the use of a governor, placed either at the meter or in proximity to the light itself. These are of many forms. Those adapted for placing near the meter are Stott’s, Fig. 49 (174 Fleet Street, E.C.), Parkinson’s, Fig. 50 (Cottage Lane Works, City Road), Strode’s, Fig. 51 (67 St. Paul’s Churchyard), Hargreaves and Bardsley’s (Hobson Street, Oldham), Hulett’s, Fig. 52 (55 High Holborn), Peebles’ (Tay Works, Edinburgh), and Smith’s (130 Fleet Street). Self-regulating burners are the “Christianson,” made by Sugg (Grand Hotel Buildings, Charing Cross), and those made by Bolding—Heran’s patent—(South Molton Street, Oxford Street), Milne, Sons, and Macfie (2 King Edward Street, E.C.), Parkinson (Fig. 53), Peebles, and Kinnear (91 Finsbury Pavement). A little steel blade, costing only a penny, is made by W. H. Howorth, Cleckheaton, Yorkshire, for use on 2-holed burners, which has the effect of silencing a roaring flame and increasing the luminosity. Another contrivance having some of the effects of a regulator, augmenting the light and consuming the smoke (therefore lessening the contamination of the air), is the Spencer Corona, Fig. 54 (3 Hyde Street, New Oxford Street), fitting closely on the top of ordinary gas globes.
50. Parkinson’s Governor.
51. Strode’s Governor.
52. Hulett’s Governor. 53. Parkinson’s Burner.
54. Spencer Corona.
The most practical methods which have been devised for combining the purity of air in a room with artificial light produced from ordinary coal gas, may be classed under four heads:—
(1) The sun burner, in which the products of combustion are removed rapidly from contact with the air of the room.
(2) The globe light, in which the fresh air is supplied and the products of combustion are removed to the outside without any contact with the air of the room.
(3) The regenerative gas light.
(4) The incandescent gas light.
Their several merits are thus discussed in one of the Health Exhibition Handbooks.
The sun burner is practically a powerful ventilator, which, by means of the great heat generated, draws a large volume of air away with the fumes of the gas; it thus relieves the air of the room of the impurities caused by combustion, and at the same time removes impurities generated from other causes. This burner is indeed a sufficiently powerful ventilator to continue acting even in the face of the counteracting draught of an open fireplace; and is consequently much used for crowded rooms. For this dual purpose, it requires to have its fumes carried up through a straight vertical tube direct to the open air. This burner is made by Strode & Co., 67 St. Paul’s Churchyard, and shown in Fig. 55.
55. The Sun Burner.
The globe light has been designed to prevent the products of combustion from mingling at all with the air of a room, but it does not provide for the ventilation of the room at the same time. The principle of the best form is that it should be burned in a glass globe separated from the air of the room; that is to say, the air required for supporting combustion is brought into the globe from the outer air, and the products of combustion are carried away into the outer air without mixing with the air of the room. This light, like the sunlight, is limited in its application. It can be placed near an outside wall, or in a room directly under a roof. If fed with fresh air from the room itself, and if a fire-proof flue be constructed in the ceiling leading into a vertical flue, this light can be put in any part of a room; but the draught from the open fire would be very likely to draw the products of combustion back into the room. This is also made by Strode & Co.
The Grimston regenerative burner looks like an inverted argand burner. The gas is brought down a central tube, and the products of combustion are carried away through a tube which lies round it, and the air required to feed the burner is brought through passages in this latter tube which are heated by the products of combustion in their course. The light is enclosed in a half globe, and the products may be carried away into the outer air, so that the light need not injure the air of the room in which it is burned. A very remarkable feature about these regenerative arrangements is that the temperature of the outflowing products of combustion at the top of the tube is so low that the hand can be held over the top of the tube without any unpleasant sensation of heat; and the combustion appears to be so perfect that even if the products are not removed from the room, there is much less unpleasantness than with ordinary gas-burners. Other very important regenerative burners are that bearing the name of F. Siemens, the Fourness (S. Gratrix, jun., and Bro., Alport Town, Manchester), and the well-known Wenham (Wenham Co., 12 Rathbone Place, W., and Milne, Sons, and Macfie, 2 King Edward Street, E.C.), two forms of which are shown in Figs. 56 and 57. Sugg’s “London Argand” and “Cromartie” burners are sufficiently familiar to need no description, and are made in a great variety of designs. The “Osborne” pattern is shown in Fig. 58.
56. Wenham Pendant Light. 57. Wenham Standard Light.
Incandescent gas lamps, even if burned in contact with the air of a room, present certain hygienic advantages. In the first place, the air required for combustion is brought into the room from the outside, in the proportion of six volumes of air to one of gas, and therefore the oxygen in the air of the room is not consumed for combustion. In the second place, the gas is consumed in a very perfect manner, so that the injury to the air of a room produced by the combustion is reduced to a minimum. These lights can be placed wherever ordinary gas-lights can, and it is probable that from the hygienic and photometric value of this class of light it is destined at no distant date to replace ordinary gas-burners. The principle of construction is as follows. In the flame of a Bunsen burner is placed a hood of cotton webbing, previously steeped in a solution containing oxides of zirconium, lanthanum, &c. The average consumption in each burner is 2 ft. gas per hour at 9/10 in. pressure, with an illuminating power of 17 candles.
The Albo-carbon light, Fig. 59, (74 James Street, Westminster), consists in superheating ordinary gas and carburetting it by admixture of the vapour generated from the albo-carbon material, which is stored in a reservoir that can be attached to any existing fittings. By its means, the light is very much intensified, steadied, and purified, at very small cost for albo-carbon with a reduced consumption of gas.
58. Sugg’s “Osborne” Burner. 59. Albo-carbon Light.
When gas has been laid on to a house, and the main connected with the meter or even before the latter has been done, it is extremely important to have all the gas-pipes tested, in order to ascertain whether any leakage exists. A very good method is as follows:—All the brackets and pendants, with one exception, are first stopped up with plugs or screwed caps, and the meter is turned off or disconnected. Upon the one outlet not stopped up a force-pump is attached, into the interstices of which have been poured a few drops of sulphuric ether. The force-pump is then connected with a gauge, and is worked until a high pressure has been registered upon it, in order that should the pipes have any latent weaknesses, the pressure exerted will develop and discover them. When the gauge indicates a certain figure, the pumping is stopped, and if the mercury is noticed to fall, it is evident that there are palpable leaks, which are at once searched for. The escaped ether will guide the operator to the whereabouts of these leaks, and the defaulting pipes are at once replaced by others. The pumping is then continued, and the same routine recommences. If the mercury still descends in the gauge glass, and the sense of smell cannot detect where the leak exists, the joints and portions of the pipes are lathered over with soap, whereupon the weak places will be found indicated by bubbles. These parts where the bubbles escape are then marked, heated by means of a portable spirit lamp made for the purpose, and covered over with a durable cement. After a short time, the pump is once more set in action, and if the pipes are tight, and the column of mercury in the gauge maintains itself at the same figure, the soundness of the pipes is assured.
An excellent portable gas-making apparatus is made by H. L. Müller, 22 Mary Ann Street, Birmingham. See also p. [998].
Matches.—An American writer, speaking of the defacement of paint by the inadvertent or heedless scratching of matches, says that he has observed that when one mark has been made others follow rapidly. To effectually prevent this, rub the spot with flannel saturated with any liquid vaseline. “After that, people may try to strike their matches there as much as they like, they will neither get a light nor injure the paint,” and, most singular, the petroleum causes the existing mark to soon disappear, at least when it occurs on dark paint. Matches should always be kept in metallic boxes, and out of the way of children and mice.
Countless accidents, as every one knows, arise from the use of matches. To obtain light without employing them, and so without the danger of setting things on fire, an ingenious contrivance is now used by the watchmen of Paris in all magazines where explosive or inflammable materials are kept. Any one may easily make trial of it. Take an oblong vial of the whitest and clearest glass, and put into it a piece of phosphorus about the size of a pea. Pour some olive oil heated to the boiling point upon the phosphorus; fill the vial about one-third full, and then cork it tightly. To use this novel light, remove the cork, allow the air to enter the vial, and then re-cork it. The empty space in the vial will become luminous, and the light obtained will be equal to that of a lamp. When the light grows dim, its power can be increased by taking out the cork and allowing a fresh supply of air to enter the vial. In winter it is sometimes necessary to heat the vial between the hands in order to increase the fluidity of the oil. The apparatus thus made may be used for six months. (Chicago Times.)
Electric Lighting.—This must not be undertaken without due knowledge or the assistance of skilled workmen. The subject is altogether too large for discussion here with any chance of making it clear and simple. The reader should refer to the works of Hospitalier and others who have made it a study. Allusion may here be made, however, to an essentially domestic system recently introduced by Hospitalier. His object is to provide 10 volt and 1½ ampère lamps operating 3 or 4 hours daily. The result aimed at is that the pile shall daily furnish a quantity of electric energy equal to that expended, and keep the accumulators continually charged. The accumulators form a reservoir, and compensate for the differences between the daily production (which is sensibly continuous) and the irregular production according to needs. This demands a continuous pile of slow discharge, in which the products consumed can be easily renewed, while repairs and supervision are minimised. The choice is a potash bichromate battery.
In a single liquid potash bichromate pile, the elements to be renewed are the zinc and the liquid which contains at once the excitant (sulphuric acid) and the depolariser (potash or soda bichromate). In order to obtain an easy renewal of the zinc, Hospitalier employs the metal in the form of a rod 18 in. in length that dips for about 3 in. only into the liquid, and that is placed in a perforated porous vessel which supports it and prevents all contact with the carbon. A certain mobility is secured to it by means of flexible attachments, so that as it wears away it descends into the liquid. Its lower extremity dips into a mass of mercury, and this keeps it amalgamated. When one rod is used up, another may be substituted for it in a few seconds. The remaining portion of the old zinc is thrown into the porous vessel. The mercury suffices to set up a perfect electric communication with the new rod that has just been introduced. The zincs are thus entirely utilised. The flow secures the continuous renewal of the exciting and depolarising liquid. The precaution to be taken is to cause the liquid to enter at the upper part, and to remove it from the lower. This prevents the elements from getting choked up, and so they may remain mounted several months, operating day and night, without any attention having to be paid to them.
The positive pole consists of three or four carbon plates which surround the porous vessel that contains the zinc, and which are connected with each other by a strip of copper and screw clamps. The connection of a zinc with the following carbon is made by means of flexible wires, in order to permit the zinc to descend into the liquid as it wears away, as has already been seen.
The four elements are mounted one above another. The liquid enters them from an earthenware reservoir of 5-6 gal. capacity, through a rubber tube. The discharge is regulated by means of a pinch-cock.
Practice has shown that it is useless to make the solution of bichromate. It is only necessary to throw some crystals into the upper reservoir and to pour into the latter some water, acidulated with a tenth of its volume of sulphuric acid. A sufficient quantity of the salt dissolves every time to assure depolarisation. The same liquid may serve 10-12 times before renewal.
There are no precise directions to be given as to the velocity of the discharge, since this must vary according to the needs of consumption. A good average is 1-1½ gal. per day. When the liquid is nearly exhausted, it is well to cause it to circulate a little more quickly. The regulation of the velocity of the flow by the Mohr pinch-cock is one of the simplest operations. After traversing the four pile elements in succession, the liquid enters glass bottles of 2 gal. capacity provided beneath with a pipe to which is affixed a rubber tube.
It is only necessary to take a full bottle, place it over the reservoir, and put the pipe into the reservoir, in order to empty it in a few minutes.
An inspection of the piles is advisable every two days. Were a larger reservoir employed and the velocity of flow moderated, the interval might be still longer.
The four elements in tension alternately charge two series of accumulators each containing three elements. This arrangement allows the use of two kinds of lamps, 6 volt ones in the cellar and small rooms, and 10 volt ones in the dining-room and office.
The cellar lamp is so arranged that it is lighted by opening the door, and extinguished by closing it. Aside from the lamps just mentioned, another is arranged for lighting a dark ante-room, and which lights up for three minutes, only, whenever a button near the door is pressed.
The use of accumulators and flowing piles presents the following advantages: (1) Convenience, the apparatus being always ready to furnish light upon turning a tap; (2) Ease of keeping in repair and of supervision, the flow and the dimensions being capable of regulation so that the consumer need look after the piles only at irregular intervals. (3) Better utilisation of the products as a result of the use of a pencil of zinc instead of wide plates. The surface attacked is reduced to the dimensions that are strictly necessary for the production of a current, and local action is thus diminished. On the other hand, the active liquor is not thrown away until completely exhausted. (4) Quality of the light. This remains steady during the entire time of the lighting, without any manipulation of the pile or any special appliance.
A few hints may be culled from Preece’s lecture on Domestic Electric Lighting, read before the Society of Arts last session.
Makers of lamps seem to consider that there is great credit in securing long life. Unfortunately, glow lamps deteriorate sadly with age. The carbon wastes imperceptibly away, and we are scarcely conscious of the fact that, after 200 or 300 hours, the lamp gives only half the light it did at first. The fact is lamps last too long. The price of a lamp should be such that we could afford to give them a short and merry life. Long life is therefore an objection.
Lamps fail in giving their light occasionally from having an imperfect vacuum. This is very easily detected by feeling the globe. If the vacuum is bad it gets quite hot. Occasionally, but very rarely, lamps explode with a loud report when the current is first put on. This is, perhaps, due to a slight leakage of air making an explosive mixture with the residual gas.
At the present moment, both the nomenclature and the efficiency of glow lamps are in a very unsatisfactory state, and we are buying pigs in a poke at a very high price.
Considerable difference of opinion exists as to the character of the globe enveloping the carbon filament. Some like them clear, some like them ground; others envelope them in shades, or make the globe of a beautiful opal glass. It is very objectionable to have the optic nerve irritated by a brilliant glowing filament; but it is equally absurd to produce a good thing and then strangle it. Grounding and shading mean loss of light. Lamps can be placed so high that they need not affect the eye, and if they do, the light can be so reflected as to be useful elsewhere. The art of lighting a room is to flood it with light without the delicate eye being offended with the direct rays from the source of light.
Switches to turn the lamps on and off are a source of great trouble in a house. As a rule, they are cheap and nasty. When fixed away from the lamps, they introduce into the circuit additional resistance, and therefore waste energy, but they are distinctly serviceable when they are fixed outside the door of a room, so that you can light it before you enter it.
In many cases the lamp is its own switch, but it is objectionable to handle a lamp, and attempts have been made to utilise the weight of the lamp itself when suspended from the ceiling to maintain contact, and to break that contact when the weight is released.
Cuts-out or safety-valves are essential to the security of a house. Short circuiting ought not to occur, but it does, and generally when showing off. It may occur when cleaning. The cut-out is so cheap and so effective that there is no excuse for its neglect. They should be fixed on every circuit.
No one must imagine that electric lighting is absolutely safe from fire. It certainly possesses elements of danger, but elements that are perfectly under control. It is very simple to secure safety if the rules and regulations to avoid fire risks be carefully followed. The simplest rule is to use nothing but the best insulated wire, and to employ none but experienced men to put it up. All accidents that have occurred have arisen from careless wiring and ignorant handling.
The design of the circuits of a house, the dimensions of conductors, the quality of the materials used, the provision against fire risks, the testing of the work done, the adaptability of means to an end, should come within the province of the professional adviser, and not be left to the successful competing contractor, however eminent the firm may be.
Estimates for furnishing electric light installations, ranging from about 3l. upwards, can be had from Messrs. Woodhouse and Rawson United, Limited, 88 Queen Victoria Street, London, E.C., and of Messrs. Appleton, Burbey, and Williamson, of 91 Queen Victoria Street, London, E.C. See also p. [1001].