Part 15

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.

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.

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.

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.

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.

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.