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.)
[Illustration: 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 1_s._ 6_d._ 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.
[Illustration: 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.
[Illustration: 50. Parkinson’s Governor.]
[Illustration: 51. Strode’s Governor.]
[Illustration: 52. Hulett’s Governor. 53. Parkinson’s Burner.]
[Illustration: 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.
[Illustration: 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.
[Illustration: 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.