Chapter VIII: Front Matter (8)

A brief allusion may be made to the mode of use of incandescent lamps for interior and private lighting. At the present time hardly any other method of distribution is adopted than that of an arrangement _in parallel_; that is to say, each lamp on the circuit has one terminal connected to a wire which finally terminates at one pole of the generator, and its other terminal connected to a wire leading to the other pole. The lamp filaments are thus arranged between the conductors like the rungs of a ladder. In series with each lamp is placed a switch and a fuse or cut-out. The lamps themselves are attached to some variety of ornamental fitting, or in many cases suspended by a simple pendant, consisting of an insulated double flexible wire attached at its upper end to a ceiling rose, and carrying at the lower end a shade and socket in which the lamp is placed. Lamps thus hung head downwards are disadvantageously used because their _end-on candle-power_ is not generally more than 60% of their maximum candle-power. In interior lighting one of the great objects to be attained is uniformity of illumination with avoidance of harsh shadows. This can only be achieved by a proper distribution of the lamps. It is impossible to give any hard and fast rules as to what number must be employed in the illumination of any room, as a great deal depends upon the nature of the reflecting surfaces, such as the walls, ceilings, &c. As a rough guide, it may be stated that for every 100 sq. ft. of floor surface one 16 candle-power lamp placed about 8 ft. above the floor will give a dull illumination, two will give a good illumination and four will give a brilliant illumination. We generally judge of the nature of the illumination in a room by our ability to read comfortably in any position. That this may be done, the horizontal illumination on the book should not be less than one candle-foot. The following table shows approximately the illuminations in candle-feet, in various situations, derived from actual experiments:--

In a well-lighted room on the floor or tables 1.0 to 3.0 c.f.
On a theatre stage 3.0 to 4.0 c.f.
On a railway platform .05 to .5 c.f.
In a picture gallery .65 to 3.5 c.f.
The mean daylight in May in the interior
of a room 30.0 to 40.0 c.f.
In full sunlight 7000 to 10,000 c.f.
In full moonlight 1/60th to 1/100th c.f.

From an artistic point of view, one of the worst methods of lighting a room is by pendant lamps, collected in single centres in large numbers. The lights ought to be distributed in different portions of the room, and so shaded that the light is received only by reflection from surrounding objects. Ornamental effects are frequently produced by means of candle lamps in which a small incandescent lamp, imitating the flame of a candle, is placed upon a white porcelain tube as a holder, and these small units are distributed and arranged in electroliers and brackets. For details as to the various modes of placing conducting wires in houses, and the various precautions for safe usage, the reader is referred to the article ELECTRICITY SUPPLY. In the case of low voltage metallic filament lamps when the supply is by alternating current there is no difficulty in reducing the service voltage to any lower value by means of a transformer. In the case of direct current the only method available for working such low voltage lamps off higher supply voltages is to arrange the lamps in series.

Additional information on the subjects treated above may be found in
the following books and original papers:--

Mrs Ayrton, _The Electric Arc_ (London, 1900); Houston and Kennelly,
_Electric Arc Lighting and Electric Incandescent Lighting_; S. P.
Thompson, _The Arc Light_, Cantor Lectures, Society of Arts (1895); H.
Nakano, "The Efficiency of the Arc Lamp," _Proc. American Inst. Elec.
Eng._ (1889); A. Blondel, "Public and Street Lighting by Arc Lamps,"
_Electrician_, vols. xxxv. and xxxvi. (1895); T. Heskett, "Notes on
the Electric Arc," _Electrician_, vol. xxxix. (1897); G. S. Ram, _The
Incandescent Lamp and its Manufacture_ (London, 1895); J. A. Fleming,
_Electric Lamps and Electric Lighting_ (London, 1899); J. A. Fleming,
"The Photometry of Electric Lamps," _Jour. Inst. Elec. Eng._ (1903),
32, p. 1 (in this paper a copious bibliography of the subject of
photometry is given); J. Dredge, _Electric Illumination_ (2 vols.,
London, 1882, 1885); A. P. Trotter, "The Distribution and Measurement
of Illumination," _Proc. Inst. C.E._ vol. cx. (1892); E. L. Nichols,
"The Efficiency of Methods of Artificial Illumination," _Trans.
American Inst. Elec. Eng._ vol. vi. (1889); Sir W. de W. Abney,
_Photometry_, Cantor Lectures, Society of Arts (1894); A. Blondel,
"Photometric Magnitudes and Units," _Electrician_ (1894); J. E.
Petavel, "An Experimental Research on some Standards of Light," _Proc.
Roy. Soc._ lxv. 469 (1899); F. Jehl, _Carbon-Making for all Electrical
Purposes_ (London, 1906); G. B. Dyke, "On the Practical Determination
of the Mean Spherical Candle Power of Incandescent and Arc Lamps,"
_Phil. Mag._ (1905); the _Preliminary Report of the Sub-Committee of
the American Institute of Electrical Engineers_ on "Standards of
Light"; Clifford C. Paterson, "Investigations on Light Standards and
the Present Condition of the High Voltage Glow Lamp," _Jour. Inst.
Elec. Eng._ (January 24, 1907); J. Swinburne, "New Incandescent
Lamps," _Jour. Inst. Elec. Eng._ (1907); L. Andrews, "Long Flame Arc
Lamps," Jour. Inst. Elec. Eng. (1906); W. von Bolton and O. Feuerlein,
"The Tantalum Lamp," _The Electrician_ (Jan. 27, 1905). Also the
current issues of _The Illuminating Engineer_. (J. A. F.)

Methods of charging.

_Commercial Aspects._--The cost of supplying electricity depends more upon the rate of supply than upon the quantity supplied; or, as John Hopkinson put it, "the cost of supplying electricity for 1000 lamps for ten hours is very much less than ten times the cost of supplying the same number of lamps for one hour." Efforts have therefore been made to devise a system of charge which shall in each case bear some relation to the cost of the service. Consumers vary largely both in respect to the quantity and to the period of their demands, but the cost of supplying any one of them with a given amount of electricity is chiefly governed by the amount of his maximum demand at any one time. The reason for this is that it is not generally found expedient to store electricity in large quantities. Electricity supply works generate the electricity for the most part at the moment it is used by the consumer. Electric lamps are normally in use on an average for only about four hours per day, and therefore the plant and organization, if employed for a lighting load only, are idle and unremunerative for about 20 hours out of the 24. It is necessary to have in readiness machinery capable of supplying the maximum possible requirements of all the consumers at any hour, and this accounts for a very large proportion of the total cost. The cost of raw material, viz. coal, water and stores consumed in the generation of electricity sold, forms relatively only a small part of the total cost, the major part of which is made up of the fixed charges attributable to the time during which the works are unproductive. This makes it very desirable to secure demands possessing high "load" and "diversity" factors. The correct way to charge for electricity is to give liberal rebates to those consumers who make prolonged and regular use of the plant, that is to say, the lower the "peak" demand and the more continuous the consumption, the better should be the discount. The consumer must be discouraged from making sudden large demands on the plant, and must be encouraged, while not reducing his total consumption, to spread his use of the plant over a large number of hours during the year. Mr Arthur Wright has devised a tariff which gives effect to this principle. The system necessitates the use of a special indicator--not to measure the quantity of electricity consumed, which is done by the ordinary meter--but to show the maximum amount of current taken by the consumer at any one time during the period for which he is to be charged. In effect it shows the proportion of plant which has had to be kept on hand for his use. If the indicator shows that say twenty lamps is the greatest number which the consumer has turned on simultaneously, then he gets a large discount on all the current which his ordinary meter shows that he has taken beyond the equivalent of one hour's daily use of those twenty lamps. Generally the rate charged under this system is 7d. per unit for the equivalent of one hour's daily use of the maximum demand and 1d. per unit for all surplus. It is on this principle that it pays to supply current for tramway and other purposes at a price which primâ facie is below the cost of production; it is only apparently so in comparison with the cost of producing electricity for lighting purposes. In the case of tramways the electricity is required for 15 or 16 hours per day. Electricity for a single lamp would cost on the basis of this "maximum-demand-indicator" system for 15 hours per day only 1.86d. per unit. In some cases a system of further discounts to very large consumers is combined with the Wright system. Some undertakers have abandoned the Wright system in favour of average flat rates, but this does not imply any failure of the Wright system; on the contrary, the system, having served to establish the most economical consumption of electricity, has demonstrated the average rate at which the undertakers are able to give the supply at a fair profit, and the proportion of possible new customers being small the undertakers find it a simplification to dispense with the maximum demand indicator. But in some cases a mistake has been made by offering the unprofitable early-closing consumers the option of obtaining electricity at a flat rate much lower than their load-factor would warrant and below cost price. The effect of this is to nullify the Wright system of charging, for a consumer will not elect to pay for his electricity on the Wright system if he can obtain a lower rate by means of a flat rate system. Thus the long-hour profitable consumer is made to pay a much higher price than he need be charged, in order that the unprofitable short-hour consumer may be retained and be made actually still more unprofitable. It is not improbable that ultimately the supply will be charged for on the basis of a rate determined by the size and character of the consumer's premises, or the number and dimensions of the electrical points, much in the same way as water is charged for by a water rate determined by the rent of the consumer's house and the number of water taps.

Wiring of houses.

Most new houses within an electricity supply area are wired for electricity during construction, but in several towns means have to be taken to encourage small shopkeepers and tenants of small houses to use electricity by removing the obstacle of the first outlay on wiring. The cost of wiring may be taken at 15s. to £2 per lamp installed including all necessary wire, switches, fuses, lamps, holders, casing, but not electroliers or shades. Many undertakers carry out wiring on the easy payment or hire-purchase system. Parliament has sanctioned the adoption of these systems by some local authorities and even authorized them to do the work by direct employment of labour. The usual arrangement is to make an additional charge of ½d. per unit on all current used, with a minimum payment of 1s. per 8 c.p. lamp, consumers having the option of purchasing the installation at any time on specified conditions. The consumer has to enter into an agreement, and if he is only a tenant the landlord has to sign a memorandum to the effect that the wiring and fittings belong to the supply undertakers. Several undertakers have adopted a system of maintenance and renewal of lamps, and at least one local authority undertakes to supply consumers with lamps free of charge.

Consumption.

There is still considerable scope for increasing the business of electricity supply by judicious advertising and other methods. Comparisons of the kilowatt hour consumption per capita in various towns show that where an energetic policy has been pursued the profits have improved by reason of additional output combined with increased load factor. The average number of equivalent 8 c.p. lamps connected per capita in the average of English towns is about 1.2. The average number of units consumed per capita per annum is about 23, and the average income per capita per annum is about 5s. In a number of American cities 20s. per capita per annum is obtained. In the United States a co-operative electrical development association canvasses both the general public and the electricity supply undertakers. Funds are provided by the manufacturing companies acting in concert with the supply authorities and contractors, and the spirit underlying the work is to advertise the merits of electricity--not any particular company or interest. Their efforts are directed to securing new consumers and stimulating the increased and more varied use of electricity among actual consumers.

All supply undertakers are anxious to develop the consumption of electricity for power purposes even more than for lighting, but the first cost of installing electric motors is a deterrent to the adoption of electricity in small factories and shops, and most undertakers are therefore prepared to let out motors, &c., on hire or purchase on varying terms according to circumstances.

A board of trade unit will supply one 8 c.p. carbon lamp of 30 hours or 30 such lamps for one hour. In average use an incandescent lamp will last about 800 hours, which is equal to about 12 months normal use; a good lamp will frequently last more than double this time before it breaks down.

A large number of towns have adopted electricity for street lighting. Frank Bailey has furnished particulars of photometric tests which he has made on new and old street lamps in the city of London. From these tests the following comparative figures are deduced:--

Average total Cost
Gas-- per c.p. per annum.
Double burner ordinary low pressure incandescent
(mean of six tests) 11.1d.
Single burner high-pressure gas 9.0
Double burner high-pressure gas 11.7
Arc lamp--
Old type of lantern 8
Flame arc 5

From these tests of candle-power the illumination at a distance of 100 ft. from the source is estimated as follows:--

Candle Ft. Ratio.
Double ordinary incandescent gas lamp
illumination 0.013 = 1.0
Single high pressure ordinary incandescent
gas lamp illumination 0.016 = 1.24
Double high pressure ordinary incandescent
gas lamp illumination 0.027 = 2.10
Ordinary arc lamp 0.060 = 4.50
Flame arc lamp 0.120 = 9.00

The cost of electricity, light for light, is very much less than that of gas. The following comparative figures relating to street lighting at Croydon have been issued by the lighting committee of that corporation:--

+----------------------+---------+------------+--------+------------+-------------+
| Type of Lamp. | Number | Distance | Total |Average c.p.|Cost per c.p.|
| |of Lamps.|apart (yds.)| Cost. | per Mile. | per annum. |
+----------------------+---------+------------+--------+------------+-------------+
| Incandescent gas | 2,137 | 80 | £7,062 | 839 | 15.86d. |
| Incandescent electric| 90 | 66 | 288 | 1,373 | 13.71 |
| Electric arcs | 428 | 65 | 7,212 | 10,537 | 11.32 |
+----------------------+---------+------------+--------+------------+-------------+

Apart from cheaper methods of generation there are two main sources of economy in electric lighting. One is the improved arrangement and use of electrical installations, and the other is the employment of lamps of higher efficiency. As regards the first, increased attention has been given to the position, candle-power and shading of electric lamps so as to give the most effective illumination in varying circumstances and to avoid excess of light. The ease with which electric lamps may be switched on and off from a distance has lent itself to arrangements whereby current may be saved by switching off lights not in use and by controlling the number of lamps required to be alight at one time on an electrolier. Appreciable economies are brought about by the scientific disposition of lights and the avoidance of waste in use. As regards the other source of economy, the Nernst, the tantalum, the osram, and the metallized carbon filament lamp, although costing more in the first instance than carbon lamps, have become popular owing to their economy in current consumption. Where adopted largely they have had a distinct effect in reducing the rate of increase of output from supply undertakings, but their use has been generally encouraged as tending towards the greater popularity of electric light and an ultimately wider demand. Mercury vapour lamps for indoor and outdoor lighting have also proved their high efficiency, and the use of flame arc lamps has greatly increased the cheapness of outdoor electric lighting.

The existence of a "daylight load" tends to reduce the all-round cost of generating and distributing electricity. This daylight load is partly supplied by power for industrial purposes and partly by the demand for electricity in many domestic operations. The use of electric heating and cooking apparatus (including radiators, ovens, grills, chafing dishes, hot plates, kettles, flat-irons, curling irons, &c.) has greatly developed, and provides a load which extends intermittently throughout the greater part of the twenty-four hours. Electric fans for home ventilation are also used, and in the domestic operations where a small amount of power is required (as in driving sewing machines, boot cleaners, washing machines, mangles, knife cleaners, "vacuum" cleaners, &c.) the electric motor is being largely adopted. The trend of affairs points to a time when the total demand from such domestic sources will greatly exceed the demand for lighting only. The usual charges for current to be used in domestic heating or power operations vary from 1d. to 2d. per unit. As the demand increases the charges will undergo reduction, and there will also be a reflex action in bringing down the cost of electricity for lighting owing to the improved load factor resulting from an increase in the day demand. In the cooking and heating and motor departments also there has been improvement in the efficiency of the apparatus, and its economy is enhanced by the fact that current may be switched on and off as required.

Testing meters.

The Board of Trade are now prepared to receive electric measuring instruments for examination or testing at their electrical standardizing laboratory, where they have a battery power admitting of a maximum current of 7000 amperes to be dealt with. The London county council and some other corporations are prepared upon requisition to appoint inspectors to test meters on consumers' premises.

Wiring rules.

All supply undertakers now issue rules and regulations for the
efficient wiring of electric installations. The rules and regulations
issued by the institution of electrical engineers have been accepted
by many local authorities and companies, and also by many of the fire
insurance companies. The Phoenix fire office rules were the first to
be drawn up, and are adopted by many of the fire offices, but some
other leading insurance offices have their own rules under which risks
are accepted without extra premium. In the opinion of the insurance
companies "the electric light is the safest of all illuminants and is
preferable to any others when the installation has been thoroughly
well put up." Regulations have also been issued by the London county
council in regard to theatres, &c., by the national board of fire
underwriters of America (known as the "National Electrical Code"), by
the fire underwriters association of Victoria (Commonwealth of
Australia), by the Calcutta fire insurance agents association and
under the Canadian Electric Light Inspection Act. In Germany rules
have been issued by the Verband Deutscher Elektrotechniker and by the
union of private fire insurance companies of Germany, in Switzerland
by the Association Suisse des électriciens, in Austria by the
Elektrotechnischer Verein of Vienna, in France by ministerial decree
and by the syndicat professionel des industries électriques. (For
reprints of these regulations see _Electrical Trades Directory_.)
(E. Ga.)

FOOTNOTE:

[1] _Journ. Inst. Elec. Eng._ 28, p. 1. The authors of this paper
give numerous instructive curves taken with the oscillograph, showing
the form of the arc P.D. and current curves for a great variety of
alternating-current arcs.

LIGHTNING, the visible flash that accompanies an electric discharge in the sky. In certain electrical conditions of the atmosphere a cloud becomes highly charged by the coalescence of drops of vapour. A large drop formed by the fusion of many smaller ones contains the same amount of electricity upon a smaller superficial area, and the electric potential of each drop, and of the whole cloud, rises. When the cloud passes near another cloud stratum or near a hilltop, tower or tree, a discharge takes place from the cloud in the form of lightning. The discharge sometimes takes place from the earth to the cloud, or from a lower to a higher stratum, and sometimes from conductors silently. Rain discharges the electricity quietly to earth, and lightning frequently ceases with rain (see ATMOSPHERIC ELECTRICITY).

LIGHTNING CONDUCTOR, or LIGHTNING ROD (Franklin), the name usually given to apparatus designed to protect buildings or ships from the destructive effects of lightning (Fr. _paratonnerre_, Ger. _Blitzableiter_). The upper regions of the atmosphere being at a different electrical potential from the earth, the thick dense clouds which are the usual prelude to a thunder storm serve to conduct the electricity of the upper air down towards the earth, and an electrical discharge takes place across the air space when the pressure is sufficient. Lightning discharges were distinguished by Sir Oliver Lodge into two distinct types--the _A_ and the _B_ flashes. The _A_ flash is of the simple type which arises when an electrically charged cloud approaches the earth without an intermediate cloud intervening. In the second type _B_, where another cloud intervenes between the cloud carrying the primary charge and the earth, the two clouds practically form a condenser; and when a discharge from the first takes place into the second the free charge on the earth side of the lower cloud is suddenly relieved, and the disruptive discharge from the latter to earth takes such an erratic course that according to the Lightning Research Committee "no series of lightning conductors of the hitherto recognized type suffice to protect the building." In Germany two kinds of lightning stroke have been recognized, one as "zündenden" (causing fire), analogous to the _B_ flash, the other as "kalten" (not causing fire), the ordinary _A_ discharge. The destructive effect of the former was noticed in 1884 by A. Parnell, who quoted instances of damage due to mechanical force, which he stated in many cases took place in a more or less upward direction.

The object of erecting a number of pointed rods to form a lightning conductor is to produce a glow or brush discharge and thus neutralize or relieve the tension of the thunder-cloud. This, if the latter is of the _A_ type, can be successfully accomplished, but sometimes the lightning flash takes place so suddenly that it cannot be prevented, however great the number of points provided, there being such a store of energy in the descending cloud that they are unable to ward off the shock. A _B_ flash may ignore the points and strike some metal work in the vicinity; to avoid damage to the structure this must also be connected to the conductors. A single air terminal is of no more use than an inscribed sign-board; besides multiplying the number of points, numerous paths, as well as interconnexions between the conductors, must be arranged to lead the discharge to the earth. The system of pipes and gutters on a roof must be imitated; although a single rain-water pipe would be sufficient to deal with a summer shower, in practice pipes are used in sufficient number to carry off the greatest storm.

_Protected Area._--According to Lodge "there is no space near a rod which can be definitely styled an area of protection, for it is possible to receive violent sparks and shocks from the conductor itself, not to speak of the innumerable secondary discharges that are liable to occur in the wake of the main flash." The report of the Lightning Research Committee contains many examples of buildings struck in the so-called "protected area."

_Material for Conductors._--Franklin's original rods (1752) were made of iron, and this metal is still employed throughout the continent of Europe and in the United States. British architects, who objected to the unsightliness of the rods, eventually specified copper tape, which is generally run round the sharp angles of a building in such a manner as to increase the chances of the lightning being diverted from the conductor. The popular idea is that to secure the greatest protection a rod of the largest area should be erected, whereas a single large conductor is far inferior to a number of smaller ones and copper as a material is not so suitable for the purpose as iron. A copper rod allows the discharge to pass too quickly and produces a violent shock, whereas iron offers more impedance and allows the flash to leak away by damping down the oscillations. Thus there is less chance of a side flash from an iron than from a copper conductor.

_Causes of Failure._--A number of failures of conductors were noticed in the 1905 report of the Lightning Research Committee. One cause was the insufficient number of conductors and earth connexions; another was the absence of any system for connecting the metallic portion of the buildings to the conductors. In some cases the main stroke was received, but damage occurred by side-flash to isolated parts of the roof. There were several examples of large metallic surfaces being charged with electricity, the greater part of which was safely discharged, but enough followed unauthorized paths, such as a speaking-tube or electric bell wires, to cause damage. In one instance a flash struck the building at two points simultaneously; one portion followed the conductor, but the other went to earth jumping from a small finial to a greenhouse 30 ft. below.

_Construction of Conductors._--The general conclusions of the Lightning Research Committee agree with the independent reports of similar investigators in Germany, Hungary and Holland. The following is a summary of the suggestions made:--

The conductors may be of copper, or of soft iron protected by galvanizing or coated with lead. A number of paths to earth must be provided; well-jointed rain-water pipes may be utilized.

Every chimney stack or other prominence should have an air terminal. Conductors should run in the most direct manner from air to earth, and be kept away from the walls by holdfasts (fig. 1), in the manner shown by A (fig. 2); the usual method is seen in B (fig. 2), where the tape follows the contour of the building and causes side flash. A building with a long roof should also be fitted with a horizontal conductor along the ridge, and to this aigrettes (fig. 3) should be attached; a simpler method is to support the cable by holdfasts armed with a spike (fig. 4). Joints must be held together mechanically as well as electrically, and should be protected from the action of the air. At Westminster Abbey the cables are spliced and inserted in a box which is filled with lead run in when molten.

_Earth Connexion._--A copper plate not less than 3 sq. ft. in area may be used as an earth connexion if buried in permanently damp ground. Instead of a plate there are advantages in using the tubular earth shown in fig. 5. The cable packed in carbon descends to the bottom of the perforated tube which is driven into the ground, a connexion being made to the nearest rain-water pipe to secure the necessary moisture. No further attention is required. Plate earths should be tested every year. The number of earths depends on the area of the building, but at least two should be provided. Insulators on the conductor are of no advantage, and it is useless to gild or otherwise protect the points of the air-terminals. As heated air offers a good path for lightning (which is the reason why the kitchen-chimney is often selected by the discharge), a number of points should be fixed to high chimneys and there should be at least two conductors to earth. All roof metals, such as finials, flashings, rain-water gutters, ventilating pipes, cowls and stove pipes, should be connected to the system of conductors. The efficiency of the installation depends on the interconnexion of all metallic parts, also on the quality of the earth connexions. In the case of magazines used for explosives, it is questionable whether the usual plan of erecting rods at the sides of the buildings is efficient. The only way to ensure safety is to enclose the magazine in iron; the next best is to arrange the conductors so that they surround it like a bird cage.

BIBLIOGRAPHY.--The literature, although extensive, contains so many
descriptions of ludicrous devices, that the student, after reading
Benjamin Franklin's _Experiments and Observations on Electricity made
at Philadelphia_ (1769), may turn to the _Report_ of the Lightning Rod
Conference of December 1881. In the latter work there are abstracts of
many valuable papers, especially the reports made to the French
Academy, among others by Coulomb, Laplace, Gay-Lussac, Fresnel,
Regnault, &c. In 1876 J. Clerk Maxwell read a paper before the British
Association in which he brought forward the idea (based on Faraday's
experiments) of protecting a building from the effects of lightning by
surrounding it with a sort of cage of rods or stout wire. It was not,
however, until the Bath meeting of the British Association in 1888
that the subject was fully discussed by the physical and engineering
sections. Sir Oliver Lodge showed the futility of single conductors,
and advised the interconnexion of all the metal work on a building to
a number of conductors buried in the earth. The action of lightning
flashes was also demonstrated by him in lectures delivered before the
Society of Arts (1888). The Clerk Maxwell system was adopted to a
large extent in Germany, and in July 1901 a sub-committee of the
Berlin Electro-technical Association was formed, which published
rules. In 1900 a paper entitled "The Protection of Public Buildings
from Lightning," by Killingworth Hedges, led to the formation, by the
Royal Institute of British Architects and the Surveyors' Institution,
of the Lightning Research Committee, on which the Royal Society and
the Meteorological Society were represented. The _Report_, edited by
Sir Oliver Lodge, Sir John Gavey and Killingworth Hedges (Hon. Sec.),
was published in April 1905. An illustrated supplement, compiled by K.
Hedges and entitled _Modern Lightning Conductors_ (1905), contains
particulars of the independent reports of the German committee, the
Dutch Academy of Science, and the Royal Joseph university, Budapest. A
description is also given of the author's modified Clerk Maxwell
system, in which the metal work of the roofs of a building form the
upper part, the rain-water pipes taking the place of the usual
lightning-rods. See also Sir Oliver Lodge, _Lightning Conductors_
(London, 1902). (K. H.)

LIGHTS, CEREMONIAL USE OF.

Non-Christian religions.

The ceremonial use of lights in the Christian Church, with which this article is mainly concerned, probably has a double origin: in a very natural symbolism, and in the adaptation of certain pagan and Jewish rites and customs of which the symbolic meaning was Christianized. Light is everywhere the symbol of joy and of life-giving power, as darkness is of death and destruction. Fire, the most mysterious and impressive of the elements, the giver of light and of all the good things of life, is a thing sacred and adorable in primitive religions, and fire-worship still has its place in two at least of the great religions of the world. The Parsis adore fire as the visible expression of Ahura-Mazda, the eternal principle of light and righteousness; the Brahmans worship it as divine and omniscient.[1] The Hindu festival of Dewali (Diyawali, from _diya_, light), when temples and houses are illuminated with countless lamps, is held every November to celebrate Lakhshmi, the goddess of prosperity. In the ritual of the Jewish temple fire and light played a conspicuous part. In the Holy of Holies was a "cloud of light" (_shekinah_), symbolical of the presence of Yahweh, and before it stood the candlestick with six branches, on each of which and on the central stem was a lamp eternally burning; while in the forecourt was an altar on which the sacred fire was never allowed to go out. Similarly the Jewish synagogues have each their eternal lamp; while in the religion of Islam lighted lamps mark things and places specially holy; thus the Ka'ba at Mecca is illuminated by thousands of lamps hanging from the gold and silver rods that connect the columns of the surrounding colonnade.

Greece and Rome.

The Greeks and Romans, too, had their sacred fire and their ceremonial lights. In Greece the _Lampadedromia_ or _Lampadephoria_ (torch-race) had its origin in ceremonies connected with the relighting of the sacred fire. Pausanias (i. 26, § 6) mentions the golden lamp made by Callimachus which burned night and day in the sanctuary of Athena Polias on the Acropolis, and (vii. 22, §§ 2 and 3) tells of a statue of Hermes Agoraios, in the market-place of Pharae in Achaea, before which lamps were lighted. Among the Romans lighted candles and lamps formed part of the cult of the domestic tutelary deities; on all festivals doors were garlanded and lamps lighted (Juvenal, _Sat._ xii. 92; Tertullian, _Apol._ xxxv.). In the cult of Isis lamps were lighted by day. In the ordinary temples were candelabra, e.g. that in the temple of Apollo Palatinus at Rome, originally taken by Alexander from Thebes, which was in the form of a tree from the branches of which lights hung like fruit. In comparing pagan with Christian usage it is important to remember that the lamps in the pagan temples were not symbolical, but votive offerings to the gods. Torches and lamps were also carried in religious processions.

Funeral lamps.

The pagan custom of burying lamps with the dead conveyed no such symbolical meaning as was implied in the late Christian custom of placing lights on and about the tombs of martyrs and saints. Its object was to provide the dead with the means of obtaining light in the next world, a wholly material conception; and the lamps were for the most part unlighted. It was of Asiatic origin, traces of it having been observed in Phoenicia and in the Punic colonies, but not in Egypt or Greece. In Europe it was confined to the countries under the domination of Rome.[2]

Christian symbolism of light.

In Christianity, from the very first, fire and light are conceived as symbols, if not as visible manifestations, of the divine nature and the divine presence. Christ is "the true Light" (John i. 9), and at his transfiguration "the fashion of his countenance was altered, and his raiment was white and glistering" (Luke ix. 29); when the Holy Ghost descended upon the apostles, "there appeared unto them cloven tongues of fire, and it sat upon each of them" (Acts ii. 3); at the conversion of St Paul "there shined round him a great light from heaven" (Acts ix. 3); while the glorified Christ is represented as standing "in the midst of seven candlesticks ... his head and hairs white like wool, as white as snow; and his eyes as a flame of fire" (Rev. i. 14, 15). Christians are "children of Light" at perpetual war with "the powers of darkness."

The early Church.

Tertullian and Lactantius.

2nd and 3rd centuries.

All this might very early, without the incentive of Jewish and pagan example, have affected the symbolic ritual of the primitive Church. There is, however, no evidence of any ceremonial use of lights in Christian worship during the first two centuries. It is recorded, indeed (Acts xx. 7, 8), that on the occasion of St Paul's preaching at Alexandria in Troas "there were many lights in the upper chamber"; but this was at night, and the most that can be hazarded is that a specially large number were lighted as a festive illumination, as in modern Church festivals (Martigny, _Dict. des antiqu. Chrét._). As to a purely ceremonial use, such early evidence as exists is all the other way. A single sentence of Tertullian (_Apol._ xxxv.) sufficiently illuminates Christian practice during the 2nd century. "On days of rejoicing," he says, "we do not shade our door-posts with laurels nor encroach upon the day-light with lamps" (_die laeto non laureis postes obumbramus nec lucernis diem infringimus_). Lactantius, writing early in the 4th century, is even more sarcastic in his references to the heathen practice. "They kindle lights," he says, "as though to one who is in darkness. Can he be thought sane who offers the light of lamps and candles to the Author and Giver of all light?" (_Div. Inst. vi. de vero cultu_, cap. 2, in Migne, _Patr. lat._ vi. 637).[3] This is primarily an attack on votive lights, and does not necessarily exclude their ceremonial use in other ways. There is, indeed, evidence that they were so used before Lactantius wrote. The 34th canon of the synod of Elvira (305), which was contemporary with him, forbade candles to be lighted in cemeteries during the day-time, which points to an established custom as well as to an objection to it; and in the Roman catacombs lamps have been found of the 2nd and 3rd centuries which seem to have been ceremonial or symbolical.[4] Again, according to the _Acta_ of St Cyprian (d. 258), his body was borne to the grave _praelucentibus cereis_, and Prudentius, in his hymn on the martyrdom of St Lawrence (_Peristeph._ ii. 71, in Migne, _Patr. lat._ lx. 300), says that in the time of St Laurentius, i.e. the middle of the 3rd century, candles stood in the churches of Rome on golden candelabra. The gift, mentioned by Anastasius (_in Sylv._), made by Constantine to the Vatican basilica, of a _pharum_ of gold, garnished with 500 dolphins each holding a lamp, to burn before St Peter's tomb, points also to a custom well established before Christianity became the state religion.

Jerome and Vigilantius.

Whatever previous custom may have been--and for the earliest ages it is difficult to determine absolutely owing to the fact that the Christians held their services at night--by the close of the 4th century the ceremonial use of lights had become firmly and universally established in the Church. This is clear, to pass by much other evidence, from the controversy of St Jerome with Vigilantius.

Vigilantius, a presbyter of Barcelona, still occupied the position of
Tertullian and Lactantius in this matter. "We see," he wrote, "a rite
peculiar to the pagans introduced into the churches on pretext of
religion, and, while the sun is still shining, a mass of wax tapers
lighted.... A great honour to the blessed martyrs, whom they think to
illustrate with contemptible little candles (_de vilissimis
cereolis_)!" Jerome, the most influential theologian of the day, took
up the cudgels against Vigilantius (he "ought to be called
Dormitantius"), who, in spite of his fatherly admonition, had dared
again "to open his foul mouth and send forth a filthy stink against
the relics of the holy martyrs" (_Hier. Ep._ cix. al. 53--_ad
Ripuarium Presbyt._, in Migne, _Patr. lat._ p. 906). If candles are
lit before their tombs, are these the ensigns of idolatry? In his
treatise _contra Vigilantium_ (_Patr. lat._ t. xxiii.) he answers the
question with much common sense. There can be no harm if ignorant and
simple people, or religious women, light candles in honour of the
martyrs. "We are not born, but reborn, Christians," and that which
when done for idols was detestable is acceptable when done for the
martyrs. As in the case of the woman with the precious box of
ointment, it is not the gift that merits reward, but the faith that
inspires it. As for lights in the churches, he adds that "in all the
churches of the East, whenever the gospel is to be read, lights are
lit, though the sun be rising (_jam sole rutilante_), not in order to
disperse the darkness, but as a visible sign of gladness (_ad signum
laetitiae demonstrandum_)." Taken in connexion with a statement which
almost immediately precedes this--"Cereos autem non clara luce
accendimus, sicut frustra calumniaris: sed ut noctis tenebras hoc
solatio temperemus" (§ 7)--this seems to point to the fact that the
ritual use of lights in the church services, so far as already
established, arose from the same conservative habit as determined the
development of liturgical vestments, i.e. the lights which had been
necessary at the nocturnal meetings were retained, after the hours of
service had been altered, and invested with a symbolical meaning.

Practice in the 4th century.

Eastern Church.

Already they were used at most of the conspicuous functions of the Church. Paulinus, bishop of Nola (d. 431), describes the altar at the eucharist as "crowned with crowded lights,"[5] and even mentions the "eternal lamp."[6] For their use at baptisms we have, among much other evidence, that of Zeno of Verona for the West,[7] and that of Gregory of Nazianzus for the East.[8] Their use at funerals is illustrated by Eusebius's description of the burial of Constantine,[9] and Jerome's account of that of St Paula.[10] At ordinations they were used, as is shown by the 6th canon of the council of Carthage (398), which decrees that the acolyte is to hand to the newly ordained deacon _ceroferarium cum cereo_. As to the blessing of candles, according to the _Liber pontificalis_ Pope Zosimus in 417 ordered these to be blessed,[11] and the Gallican and Mozarabic rituals also provided for this ceremony.[12] The Feast of the Purification of the Virgin, known as Candlemas (q.v.), because on this day the candles for the whole year are blessed, was established--according to some authorities--by Pope Gelasius I. about 492. As to the question of "altar lights," however, it must be borne in mind that these were not placed upon the altar, or on a retable behind it, until the 12th century. These were originally the candles carried by the deacons, according to the _Ordo Romanus_ (i. 8; ii. 5; iii. 7) seven in number, which were set down either on the steps of the altar, or, later, behind it. In the Eastern Church, to this day, there are no lights on the high altar; the lighted candles stand on a small altar beside it, and at various parts of the service are carried by the lectors or acolytes before the officiating priest or deacon. The "crowd of lights" described by Paulinus as crowning the altar were either grouped round it or suspended in front of it; they are represented by the sanctuary lamps of the Latin Church and by the crown of lights suspended in front of the altar in the Greek.

Development of the use.

To trace the gradual elaboration of the symbolism and use of ceremonial lights in the Church, until its full development and systematization in the middle ages, would be impossible here. It must suffice to note a few stages in the process. The burning of lights before the tombs of martyrs led naturally to their being burned also before relics and lastly before images and pictures. This latter practice, hotly denounced as idolatry during the iconoclastic controversy (see ICONOCLASM), was finally established as orthodox by the second general council of Nicaea (787), which restored the worship of images. A later development, however, by which certain lights themselves came to be regarded as objects of worship and to have other lights burned before _them_, was condemned as idolatrous by the synod of Noyon in 1344.[13] The passion for symbolism extracted ever new meanings out of the candles and their use. Early in the 6th century Ennodius, bishop of Pavia, pointed out the three-fold elements of a wax-candle (_Opusc._ ix. and x.), each of which would make it an offering acceptable to God; the rush-wick is the product of pure water, the wax is the offspring of virgin bees,[14] the flame is sent from heaven.[15] Clearly, wax was a symbol of the Blessed Virgin and the holy humanity of Christ. The later middle ages developed the idea. Durandus, in his _Rationale_, interprets the wax as the body of Christ, the wick as his soul, the flame as his divine nature; and the consuming candle as symbolizing his passion and death.

In the Roman Catholic Church.

Dedication of a church.

At Mass and choir services.

Sanctuary lamps.

Symbol of the Real Presence.

In the completed ritual system of the medieval Church, as still
preserved in the Roman Catholic communion, the use of ceremonial
lights falls under three heads. (1) They may be symbolical of the
light of God's presence, of Christ as "Light of Light," or of "the
children of Light" in conflict with the powers of darkness; they may
even be no more than expressions of joy on the occasion of great
festivals. (2) They may be votive, i.e. offered as an act of worship
(_latria_) to God. (3) They are, in virtue of their benediction by the
Church, _sacramentalia_, i.e. efficacious for the good of men's souls
and bodies, and for the confusion of the powers of darkness.[16] With
one or more of these implications, they are employed in all the public
functions of the Church. At the consecration of a church twelve lights
are placed round the walls at the twelve spots where these are
anointed by the bishop with holy oil, and on every anniversary these
are relighted; at the dedication of an altar tapers are lighted and
censed at each place where the table is anointed (_Pontificale Rom._
p. ii. _De eccl. dedicat. seu consecrat._). At every liturgical
service, and especially at Mass and at choir services, there must be
at least two lighted tapers on the altar,[17] as symbols of the
presence of God and tributes of adoration. For the Mass the rule is
that there are six lights at High Mass, four at a _missa cantata_, and
two at private masses. At a Pontifical High Mass (i.e. when the bishop
celebrates) the lights are seven, because seven golden candlesticks
surround the risen Saviour, the chief bishop of the Church (see Rev.
i. 12). At most pontifical functions, moreover, the bishop--as the
representative of Christ--is preceded by an acolyte with a burning
candle (_bugia_) on a candlestick. The _Ceremoniale Episcoporum_ (i.
12) further orders that a burning lamp is to hang at all times before
each altar, three in front of the high altar, and five before the
reserved Sacrament, as symbols of the eternal Presence. In practice,
however, it is usual to have only one lamp lighted before the
tabernacle in which the Host is reserved. The special symbol of the
real presence of Christ is the _Sanctus_ candle, which is lighted at
the moment of consecration and kept burning until the communion. The
same symbolism is intended by the lighted tapers which must accompany
the Host whenever it is carried in procession, or to the sick and
dying.

As symbols of light and joy a candle is held on each side of the
deacon when reading the Gospel at Mass; and the same symbolism
underlies the multiplication of lights on festivals, their number
varying with the importance of the occasion. As to the number of these
latter no rule is laid down. They differ from liturgical lights in
that, whereas these must be tapers of pure beeswax or lamps fed with
pure olive oil (except by special dispensation under certain
circumstances), those used merely to add splendour to the celebration
may be of any material; the only exception being, that in the
decoration of the altar gas-lights are forbidden.

Tenebrae.

In general the ceremonial use of lights in the Roman Catholic Church
is conceived as a dramatic representation in fire of the life of
Christ and of the whole scheme of salvation. On Easter Eve the new
fire, symbol of the light of the newly risen Christ, is produced, and
from this are kindled all the lights used throughout the Christian
year until, in the gathering darkness (_tenebrae_) of the Passion,
they are gradually extinguished. This quenching of the light of the
world is symbolized at the service of _Tenebrae_ in Holy Week by the
placing on a stand before the altar of thirteen lighted tapers
arranged pyramidally, the rest of the church being in darkness. The
penitential psalms are sung, and at the end of each a candle is
extinguished. When only the central one is left it is taken down and
carried behind the altar, thus symbolizing the betrayal and the death
and burial of Christ. This ceremony can be traced to the 8th century
at Rome.

The Paschal Candle.

On Easter Eve new fire is made[18] with a flint and steel, and
blessed; from this three candles are lighted, the _lumen Christi_, and
from these again the Paschal Candle.[19] This is the symbol of the
risen and victorious Christ, and burns at every solemn service until
Ascension Day, when it is extinguished and removed after the reading
of the Gospel at High Mass. This, of course, symbolizes the Ascension;
but meanwhile the other lamps in the church have received their light
from the Paschal Candle, and so symbolize throughout the year the
continued presence of the light of Christ.

Baptism.

Ordination, etc.

Funeral lights.

At the consecration of the baptismal water the burning Paschal Candle
is dipped into the font "so that the power of the Holy Ghost may
descend into it and make it an effective instrument of regeneration."
This is the symbol of baptism as rebirth as children of Light. Lighted
tapers are also placed in the hands of the newly-baptized, or of their
god-parents, with the admonition "to preserve their baptism inviolate,
so that they may go to meet the Lord when he comes to the wedding."
Thus, too, as "children of Light," candidates for ordination and
novices about to take the vows carry lights when they come before the
bishop; and the same idea underlies the custom of carrying lights at
weddings, at the first communion, and by priests going to their first
mass, though none of these are liturgically prescribed. Finally,
lights are placed round the bodies of the dead and carried beside them
to the grave, partly as symbols that they still live in the light of
Christ, partly to frighten away the powers of darkness.

Excommunication.

Conversely, the extinction of lights is part of the ceremony of
excommunication (_Pontificale Rom._ pars iii.). Regino, abbot of Prum,
describes the ceremony as it was carried out in his day, when its
terrors were yet unabated (_De eccles. disciplina_, ii. 409). "Twelve
priests should stand about the bishop, holding in their hands lighted
torches, which at the conclusion of the anathema or excommunication
they should cast down and trample under foot." When the
excommunication is removed, the symbol of reconciliation is the
handing to the penitent of a burning taper.

Protestant Churches.

As a result of the Reformation the use of ceremonial lights was either greatly modified, or totally abolished in the Protestant Churches. In the Reformed (Calvinistic) Churches altar lights were, with the rest, done away with entirely as popish and superstitious. In the Lutheran Churches they were retained, and in Evangelical Germany have even survived most of the other medieval rites and ceremonies (e.g. the use of vestments) which were not abolished at the Reformation itself.

Church of England.

The "Lincoln Judgment."