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ilp archive : journals

public lighting no. 21 vol. 6
April-June 1941

Editorial p21
The season of black-out has passed. The Lighting Engineer stands by yearning for the day when the Lighting Order is withdrawn and he once again can serve his fellow countrymen by supplying that much needed blessing - light. "Wonder of wonders, the town we were at had no 'black-out'. My word, it was grand to see the night lights again, and you can guess how good it was to see them all twinkling again in the distance when we returned to the ship at night."
Lighting: ARP

Dual Form Of Lighting p21
Pretoria, South Africa, is a pioneer of a new form of street lgithing. The scheme employs two forms of electric discharge lighting. At the head of the standard is a 400W high pressure mercury vapour lamp and on a gallery beneath is ranged twelve sections of fluorescent tubing with total wattage of 440 watts. The combination of two district units gives a good colour, and a light from which glare is reduced to a minimum. The distinctive decorative designe lends itself to the illumination of municipal buildings, open spaces, and similar places.
Lighting: Installations, Lighting: Lamps, Lighting: Luminaires

The 80W Fluorescent Lamp p21
Considerable attention has been given to the development of the fluorescent lamp for internal illumination. Many advantages have been claimed with its use that it is likely it will be used for street lighting. Its relatively great length might at first appear to be a disadvantage; in practice, it is found possible to produce a shadow-free light.
Lighting: Lamps

Unmasking The Traffic Lights p21
Complaints are heard on every hand of the difficulties experienced in distingushing the colour of masked traffic signals in daylight and, in particular, in bright sunshine. On a bright day the road traffic light has practically lost its real value in giving timely warning. The masks, fitted as a war-time measure, should be regarded by the authorities as a "winter-time" restriction.
With the introduction of a "two-hour" summertime, daylight is available to the motorist until a late hour, whilst during the hours of actual darkness very few people use the roads. It should be possible for masks to be removed entirely during "summer time" and at a late hour, the traffic light should be extinguished, except at a few important traffic centres or vital crossings.
(There is nothing novel in the latter suggestion, for it is the practice of many districts, including London, to extinguish traffic lights soon after official black-out time).
It would appear a simple matter for traffic light masking to come under control of the Public Lighting Engineer. His department is organised to maintain a watch on all types of street lighting in his area, and it would need little extra organisation to detail lamplighters with the task of masking or unmasking traffic lights during the period of "winter-time" lighting.
Lighting: ARP

Describing A New Light Source p22
A new light source has been announced - the fluorescent tube. Just imagine a tube 5 ft. long and 1½ ins. diameter, glowing throughout its whole length with a bright white light nearer to natural daylight than any other source. Then it will be appreciated that the Osira fluorescent tube is not just another new kind of lamp; it is a new conception in artificial light values.
Its many attractive characteristics are given in a new leaflet, just issued by the GEC. In addition, fittings and auxiliary gear have also been developed for use with the lamp.
Lighting: Lamps

War Damage Act, 1941 p22
Many enquiries have been made concerning the exact position of a Public Lighting Department under the terms of the War Damage Act.
It provides that payments are to be made by the War Damage Commission to Highway Authorities under a scheme to be made by the Treasury in respect of war damage to highways maintainable at the public expense during the risk period. The scheme may also provide for payments by the Commission in respect of War Damage to roads not being highways maintainable at the public expense (generally known as private roads) in cases in which works for making good such damage are executed by highway authorities.
Contribution towards the expense of the payments are to be made by Counties and County Boroughs by five annual installments commencing with the present year, and one final installment.
Lamps, lamp posts, or other materials or apparatus fixed on or near to a highway for the purpose of illuminating it, and traffic signs, are deemed to form part of the highway. It is apparent that lamps, bollards and traffic signs are covered in respect to war damage, but not such erections as fire alarm posts, water stand pipes or tramway standards.
Lighting: ARP, Lighting: Funding

New Portable Lamp Aids Rescue Work p22
After a generator and searchlight were instrumental in the rescue of a woman and her child after a bombing raid, the local Emergency Committee decided that all rescue parties under its control should be equipped with portable lighting equipment. Naked flares were ruled out on account of the danger of possible gas leakages or burst mains. Suggestions were invited and within 24 hours a design was submitted to the committee. It was a simple affair of five 12V 12W Osram gas-filled "bus lamps" mounted in a dispersive-type reflector and connected to an adjustable stand by a knuckle joint. Current was supplied by a 51AH accululator giving 10 hours continuous light per charge. The design was unanimously approved and in less than three weeks 50 complete sets were delivered. Since that time the lamps have proved invaluable for rescue work.
Lighting: ARP

Bollards In The Black-Out Contributed by C. H. Winstone p23
BS ARP/37 largely ignores traffic requirements and is intended almost entirely for the benefit of the pedestrian. The lighting of traffic bollards and other obstructions is now of major importance since by their own internal illumination only are they revealed to drivers.
It remains a fact that very many accidents do occur as a result of collisions with refuges etc.
These have reduced in number. The reasons may be: (1) Smaller number of vehicles on the road; (2) Drivers are becoming accustomed to driving under black-out conditions; (3) Bollards are receiving more careful attention and are illuminated by less haphazard methods. The last is the only under control of the Lighting Engineer and he's confined within limits defined by the Ministry Of Home security regulations.
This extract from the Lighting (Restriction) Order, 1940, gives the following regulations:
  • 6. The following lights may be displayed for the guidance of traffic on roads :-)
    • (c) A light in the head of a bollard on a refuge so long as -
      • (i) The light is screened so that no illumination falls on the stem of the bollard.
      • (ii) No light is emitted through any panel in the head of the bollard facing towards the centre of the refuge.
      • (iii) Any illuminated panel not facing towards the centre of the refuge is screened from above and so dimmed that, while it is clearly visible at a distance of 100 feet, it is inconspicuous at 250 feet.
      • (iv) In the case of any illuminated panel bearing words, the letters appear white on a dark background, and
      • (v) Illuminated panels not bearing words are white.
    • (d) Lights indicating the position of a refuge or of the circumference of the centre island of a roundabout, so long as -
      • (i) Each light is hooded so as to prevent light being thrown upwards.
      • (ii) All apertures for the emission of light are in the form of right-angled crosses of which the arms are at an angle of 45 degrees to the horizontal and are four inches in length over all and half an inch in width.
      • (iii) Each aperture is screened so that the brightness of the cross is substantially uniform over its whole area and does not exceed 0.5 candle per square foot and
      • (iv) the light is white.
With the important exception of (c) (iii), each item is a positive instruction. To require a panel to be so illuminated that it is clearly visible at 100 feet and inconspicious at 250 is far from "laying down the law" as it is usually understood. It has been suggested that a standard of brightness might be added to the regulation to indicate the brightness necessary to meet this requirement but under the variable circumstances applying to these cases this is obviously impossible. Among the variables are : (1) The human eye (2) Weather conditions (3) Time of night (4) Background (5) Size of panel, and lettering Figures of brightness might perhaps be quoted as a guide only, for various types of panels, and an average brightness could be between 0.5 and 1.5 equivalent foot-candles (or foot-lamberts). Obviously the larger the panel the lower the brightness necessary to make the sign visible at a given distance.
Very often the general public will decided whether the panel is too bright and by conveying its decision to the police, will upset completely all the work which the Lighting Engineer has carried out.
The actual illumination of the head of a bollard presents a number of problems. If the side panels are of the same size as the front panenl, and the latter is lettered, much less light will be required on the white side panels than on the front. It is almost impossible to provide a real white light from either gas or electric sources which is sufficiently "poor" in lumen output to meet the regulations.
Probaly the cheapest and most effectively way is to convert the small light source into a large diffusing source and then to mask the large source until the illumination is reduced sufficiently. Indirect methods of lighting are also of value.
It is suprising to find that a large number of bollards have only the front "Keep Left" panels illuminated, and although the Ministry of Home Security regulations allow the side panels to be illuminated, these have been blacked out. It is possible, at night time, for a bollard with only the front panel illuminated to be completely indistinguishable to drivers from certain positions. To conform with present day practice it would seem advisable to utilise the St. Andrew's Cross sign, as the portion to be illuminated in the side panels, and every illuminated bollard should be fitted in this manner.
Particular attention should be paid to the constructional details of hoods fitted to illuminated bollards to screen the panels from above. The hoods fitted to screen the light should be as small as possible because the distance from the front edge of the bollard to the nearest edge of the refuge is only a matter of a few inches, which means that a large hood would continually be in a damaged state through being hit by vehicles turning at the bollard. Large hoods also prevent clear observation from the higher driving seats of lorries and public transport vehicles.
There are many types of small lamps, with an illuminated St. Andrews's Cross, on each of the three sides available for attaching to unlighted bollards.
It is evident, therefore, that the Public Lighting Engineer has plenty of scope in providing illumination of road obstructions so that they are clearly visible at all angles on the roadway in spite of the low degree of light output allowed.
Lighting: ARP, Lighting: Levels, Lighting:Signs

Improved Lighting For Factory Workers p24
Picture of fluorescent tube installation in sheet steel factory.
Lighting: Lamps

A Distinctive Outdoor Lighting System p25
Some time ago, the Pretoria Municipality invited the submission of competitive designs of a complete lighting scheme for its most important civic centre - Church Square. Sone scheme was rather off the beaten track. It was a distinctive design and employed two forms of electric discharge lighting - its efficacy was one of the reasons the scheme was chosen. It was submitted by The British General Electric Company Limited of Johannesburg.
At the extreme top of the standard is a sphere 20 ins. in diameter which houses a 400W high pressure mercury vapour lamp. On the gallery is a unit comprising twelve sections of white Osira fluorescent tubing. Each section is six feet in length, the total wattage of the unit being approximately 440W. The combination of these two units gives a light of extremely good colour with minimal glare. These features coupled with the carefully chosen mounting height provide an even illumination over a relatively large area. (The minimum illumination is 0.5 foot-candles with the maximum being 2 foot-candles).
There are 60 of these units located about 70' apart in and around Church Square.
Lighting: Installations, Lighting: Lamps, Lighting: Luminaires

The Association Of Public Lighting Engineers p26
The Annual Conference, a special feature of the Association, is for the time being relegated to the ever-increasing list of "after the war" events.
Members of the Association have played an important part in organising for the defense of the civil population. In the majority of cases, this includes the lighting of air raid shelters, installation of special street signs, bollards etc., and to install the new schemes of war-time street lighting.
At a recent meeting of the Council of the Association it was unanimously agreed that the organisation should be kept intact, but it was considered unwise to call members together in London. In the last Annual General Meeting, it was agreed that the work of the Association should be left in the hands of the existing council until the end of the war or until the next AGM.
Since the outbreak of war, the Association has been represented on the Joint Lighting Committee of the Ministry of Home Security. The members of this Committee have been able to contribute valuable technical assistance in producing the now familiar BS/ARP 37 low-intensity lighting unit, which is now installed in all the principal cities, but they have been privileged to help in many other directions where war-time lighting restrictions have been concerned. The work of the Committee also incldued the specifications for the lighting of bollards, motor-car headlights, air raid shelter lighting, etc. The exhaustive experimental work carried out has provided the technical lighting experts with much valuable information.
Early in 1940, the Association, in close collaboration with the Council of Iluminating Engineering Society, arranged a series of meetings in Westminster, for the sole purpose of demonstrating a complete area installed with the BS/ARP 37 units - with gas and electricity. The demonstration was held in Westminster and was a complete success with representatives from 600-700 local authorities attending.
Mr. Percy Good, chairman of the Joint Lighting Committee, was an untiring working throughout the experimental stages of the new lighting. Technical explanatory details of BS/ARP 37 were given by Mr. F. C. Smith, M.Inst.G.E., and convincing demonstrations of the lighting were projected on a screen by Mr. J. M. Waldram, B.Sc. The demonstration in Westminster was arranged by C. I. Winstone of the Gas, Light and Coke Company. So successful were the demonstrations that similar meetings were held in Leicester, with Mr. Thomas Wilkie providing a comprehensive display.
APLE: Conference, APLE: Organisation, Lighting: ARP, Lighting: Personnel

New Members p26
List of new members of the APLE.
APLE: Organisation

The Burning Position Of Mercury Discharge Lamps p27
A question sometimes asked about high-pressure mercury discharge lamps refers to the burning position i.e. whether it is detrimental to the life and efficiency of the lmaps if they are installed and operated in any position out of the normal cap upwards position.
The answer is "Yes" and "No" according to the wattage of the lamps being installed.
In the case of 250W and 400W lamps, both the useful life of the lamp and the light output will be adversely affected if burned at any appreciable angle out of the vertical. Special lamps are required for different angles - these are available but not recommended since they do not give the same high efficiency. The 80W and 125W lamps of the 3-pin type are not so sensitive. These can be burned vertically (cap up) or horizontally or any angle without deleterious effect on life or light output.
The past winter has taught many lessons especially how important it is to provide good internal lighting. What was considered adequate artificial lighting before the war is now considered inadequate. One reason is that many people now spend much more time in factories that are lighted artifically during the day as well as during the hours of darkness. Municipal officials and business house executivies now realise the nearer to natural daylight the artificial lighting is then the smaller will be the ill-effects on working staff. More and more establishments are now being lit by Osira 5-ft fluorescent tubes. When one consideres the other valuable features of this discharge tube - its high efficiency, its economy of current (80W) and its low heat generation - it is not surprising that it is being approved all over the country as the main illuminant in Government and municipal offices and business establishments generally.
Lighting: ARP, Lighting: Lamps

Mazda 80-watt 60-in. Fluorescent Lamp p28
Recently BTH produced a new form of lamp which has revolutionised the science and art of lighting.
Fluorescent materials have the property of changing the wavelength of light, and consequently its colour. Each fluorescent material has the property of changing the wavelength of any impinging or transmited light to one particular value regardless of the original wavelength. By choosing suitable fluorescent material or mixture of materials, it follows that any desired quality of light can be obtained. The new lamp produces a large amount of light at 2537° and the purpose of the fluorescent powder which coats the tube is to convert this invisible light into visible light of approximate daylight quality.
The lamp consists of a glass tube 5 ft. long and 1½ins. diameter, coated on the inside surface with a think layer of a mixture of fluorescent powders. It is filled with argon at a pressure of about 1/200th of an atmosphere and has a small amount of mercury. The temperature at which the lamp operates is so low 40°C, that the fluorescent powder can be safely placed on the inner surface of the tube and no outer jacket is required.
Owing to the long length of the lamp, it is necessary to heat the electrodes so they emit a copious supply of electrons and then to give a voltage surge to enable the arc to strike. Once the arc has struck, the current flows freely, and would build up to destructive levels if there were not also a choke which functions as a current limiter. The electrodes need only be heated for an instant and the voltage surge is only required momentarily. Both these requirements are met by means of a thermal starter switch.
On switching on, the current flows through the choke, the heater coil, the electrodes and the starter switch contact and back to line. The electrodes are heated and at the same time the heated coil is heated, which in turn heats the bi-metal of the switch. When the bi-metal has been heated, the contacts break and so cause a voltage surge due to the presence of the choke in the circuit, this surge causing the arc to strike.
The efficiency of the lamp is high, the initial value being 35 lumens per watt, and its brightness is low, due the fact that the total light output is evenly spread over a comparatively large area. The brightness figure is about 3 candles per square inch, so the lamp is practically free from glare.
Like all discharge lamps, the new lamp is capable of producing a stroboscopic effect, but to a much smaller degree, since the fluorecent powders have some degree of phosphorescence which introduces a damping effect. The effect is approximately intermediate between an incandescent lamp and standard discharge lamp.
The new lamp has many advantages over the older types of lamp and would appear to have no disadvantages. Its relatively great length, is now seen as an advantage, in that it makes it possible to produce shadow-free light.
Although the lamp has many applications, industrial lighting in present circumstances must take precedence.
Lighting: Lamps

Portalux p29
From the industrial workshop point of view, the Ediswan Portalux lighting unit for 5' 80W fluorescent discharge tubes is the most important development in this field of lighting since its introduction last year. Its portability and adaptability, to vertical or horizontal position, the "Portalux" enables daylight to be brought up, in, or under the work. It turns a five-foot tube into a hand inspection lamp.
The "Portalux" unit consists of an Ediswan trough reflector carried in a tubular steel frame which is mounted on a heavy cast iron base; the reflector is made from sheet steel; the lamp holders are resiliently mounted into felt to protect the lamp against vibration and shock. A detachable cover fitted with armour plate glass is provided to keep the reflector and lamp clean nad to protect the lacquered surface of the reflector against damage.
The unit is entirely self contained and requires only the fixing of the 3-core supply cable to the switch terminal. The cast iron base houses a choke, condenser and other components of the lamp control equipment, while in the tubular frame are arranged a double pole switch and internal wiring.
The finish is appropiate to the workshop in grey glossy stove synthetic enamel; the reflector has a reflecting surface or white glossy stove synthetic enamel.
Lighting: Lamps, Lighting: Luminaires

Rebuilding Our Cities p29
In place of haphazard designs of street columns, which so often mar the appearance of a thoroughfare, may there be seen in the future, lamp columns with a display of dignity in design, and artistry in their placing. It is now a rule that designs of public buildings shall have the approval of the Fine Arts Commissioners, to whom designs are submitted. The commissioners spent considerable time some months ago, examining designs of street lighting columns submitted to them from manufacturers through the APLE. The suggestions they put forward and the modifications made by the designers resulted in a set of extremely satisfactory designs being approved and made available.
It is hoped that in any new scheme for street improvements and reconstruction after the war, lamp column design will be considered as a definite part of the whole scheme.
Lamp column manufacturers now have a range of approved designs.
Lighting: Design

Saving Precious Minutes p30
Description of the Tong Test ammeter from Crompton Parkinson Limited.

Trade Notes p30
The Ediswan Industra publication No. L.E.1162 has been published to include new lighting developments arising out of the new factory lighting regulations and the introduction of the 80W fluorescent tube. It is a lighting handbook with complete catalouge of fittings required for industrial lighting.
Lighting: Publications

An Interesting Achievement With Fluorescent Tubular Lamps p30
A vital chemical process in a Government factory involves the addition of acids to a liquid solution by carefully controlled stages, as a result the liquid changes in colour. The operation is so critical it could normally only be carried out under the most favourable daylight conditions. The introduction of the fluorescent tube promised an opportunity of providing controlled light closely resembling daylight. Investigation showed that an illumination of 120/150 foot candles over a working area of 6' x 4' would be necessary to provide sufficient illumination. A special fitting was designed to accommodate four 80W Crompta lamps, made from sheet brass with chromium plated reflecting surface, the exteriod being painted with acid-resistant material. The process may now be continued day and night without interruption.
Lighting: Lamps

Personalia p30
Notices of retirements, promotions and new appointments.
Lighting: Personnel

Good Lighting p31
Pre-war pictures of installations in Folkestone, Bath Road and Hampstead.
Lighting: Installations

In Parliament p32
From a statement made by Mr. Herbert Morrison in the House Of Commons on the 24th last month, there is little prospect of a material change in the street lighting regulations. He was asked if there would be any increase in the standard of illumination next winter and he replied that the investigations made last year indicated that no increase was possible in the existing circumstances, and added that the question for further steps next winter must depend on the strategical situation. While the Prime Minister had indicated that an improvement would be effected, his statement was followed by heavy air attacks which imposed a revision of the plans then in view. "Public opinion would be ratehr apprehensive as things are if there were any increase in lighting."
Lighting: ARP, Lighting: Legal

Do You Remember? Lights Up Order p32
Instructions were telegraphed last evening by the Home Office to the police authorities with regard to the relaxation of the lighting restrictions. They are "The masking of street lamps may be removed, but, in view of the coal shortage, the total number of lamps in use should not exceed one-half of the normal. The shading of lights in houses and shops may be withdrawn, but the prohibition of lights in shop windows and of advertisement lights, must be maintained on account of the coal shortage. The question of lights on vehicles is under consideration and, for the present, the existing Orders remain in force." - The Daily Chronicle, November 12th, 1918
Lighting: ARP, Lighting: History

Classified List Of British Standard A.R.P. Specifications p32
List of ARP publications of interest to lighting engineers.
Lighting: ARP

maintenance Of Efficient Lighting p32
A proportion of failing light during servcie is avoidable. Lamps will normally deteriorate in efficiency. To maintain maximum output of light, measurements should be taken periodically. It is the practice in well-organised public lighting departments for a record of each lamp to be kept, the lamp being taken down and light output tested.
Quite independent of the usefyl life of the light source, is it generally realised how deleterious is the effect of dirty lamps, dirtly reflectors etc. Government investigations carried out in various workshops resulted in an increase of nearly 2½ times the light. Dirt may account for more than half of the light.
Lighting: Maintenance

The Annual Report p32
At the request of a Government Departmetn, the Council of the APLE has been asked to increase the usefulness of the statistical returns, which is a feature of the report, to include added information. It has been suggested that information should be given as far as possbile from all lighting authorities in the country.
They look to the members to supply this information as quikcly as possible. The report in its enlarged form will prove an expensive outlay, but the Council is of the opinion that such a volume of information must prove of infinite value to all concerned when post-war problems come under review.
Information asked for will include: Official in charge of public lighting; population; number of lighting employees; number of lamps; miles lighted; miles unlighted; aggregate consumption per annum; method of control; nominal mounting heights of lamps; number of columns: steel, cast iron, concrete, wall brackets, other types; expenditure. All statistics should be given for both gas and electricity.
Lighting: Statistics, APLE: Journal

Adverts: The General Electric Co., Ltd, William Sugg And Co., Ltd., Siemens Electric Lamps And Supplies Ltd., Metropolitan Vickers Electrical Co. Ltd, British Commercial Gas Association, The British Thomson-Houston Co. Ltd., British, Foreign And Colonial Automatic Light Controlling Co., Ltd., APLE, Public Lighting and The General Electric Co., Ltd.