It is backed by extensive practical experience and is a throughly reliable product, guaranteed by The General Electric Comapny, Ltd., and approved by experienced electrical engineers and lighting authorities.

Some general notes and technical practicalities of the OSIRA lamp will be found on pages 24-30. We shall be pleased to forward more detailed information on the lamp and its application to those interested in special lighting problems.

The New Light Source
The OSIRA electric discharge lamp constitutes the most important recent advance in the technique of light production.

In the past all practical illuminants have depended upon the radiation emitted from heated bodies. The sun, the filament of an electric lamp, the gas mantle and the crater of a carbon arc, all emit light because, and only because, they are extremely hot. There is a limit to the efficiency obtainable from such sources; in a metal filament lamp, for example, as the melting point of tungsten is approached.

The case of electric discharge lamps is entirely different. The light is produced not because the gas or vapour is very hot, but because it is "excited" electrically. The limits of efficiency are greatly in excess of those obtainable from heated bodies. The OSIRA lamp gives is light by the discharge of electricity through a mixture of gases, which includes mercury vapour at a higher pressure than has hitherto been practical. The lamp can be run directly off ordinary A.C. mains, the only essential auxiliary being a series impedance.

Development And Trials
The OSIRA lamp was invented and developed in the Research Laboratories of The General Electric Company, Ltd. at Wembley, Middlesex, and was first put into operation on June 22nd, 1932, for street lighting in the G.E.C. installation in East Lane, Wembley. This was the first public lighting installation in the world to employ lamps of this type, and they may be said to have left the laboratory stage at this time.

The First Service Installation
The outdoor trials in East Lane were followed by a complete installation operating under normal electric conditions on the Watford Road, Wembley. These 46 units were erected by The North Metropolitan Electric Power Supply Company for the Wembley Urban District Countil and were put into service at the beginning of March 1933. The whole of the equipment operated satisfactorily from the outset, thus providing that OSIRA lamps were practical, reliable, and efficient under service conditions.

Practical Applications
The list of districts where OSIRA lamps have been specified for public lighting in conjunction with G.E.C. lanterns and equipment is continually growing. Among pioneer installations of these lamps are thjose at :-

The introduction in 1934 of the 250-watt OSIRA lamp has enabled secondary roads to be provided with the same quality of lighting as the main roads which employ the 400-watt lamp, though at a a lower level of brightness.

The general construction and principles of the 250-watt OSIRA lamp are similar to those of the 400-watt, the light output being, for each lamp, roughtly 2½ tiems that which would be given by a tungsten filament lamp of the same wattage. The principal characteristics of both lamps are given in the technical notes.

G.E.C. Lanterns For OSIRA Lamps
The OSIRA lamp, being fitted with a standard G.E.S. cap, can be used in many existing fittings, providing care is taken to protect the lamp from water drips or driving rain.

The source, however, differs widely in shape from that of a filament lamp, and if the full efficiency of the OSIRA lamp is to be utilised special fittigns are essential.

The G.E.C. Laboratories and Illuminating Engieners have been engaged on this problem since 1932, and a series of special lanterns have been designed to give the most effective distribution of light on the surface of the roadway. These lanterns are illustrated and described on pages 13-21. Further fittings are still under development.

Street Lighting
"Accident-proof" street lightin is needed to-day as never before. The OSIRA lamp puts lighting of this class within the reach of all lighting authorities. The ability to provide over double the light for the same energy consumption gives to the electrical engineer an advantage which makes older forms of illuminant definitely obsolete.

It is gratifying to record in this connection that the numerous lighting authorities who have so far completed or are installing OSIRA street lighting units ar eusing them, not to reduce expenditure, but to improve on the existing installations.

The stirking improvement which the new lamp makes possible is borne out by the typical photographs reproduced within this publication.

Realising the fact that, for the same light output, the OSIRA lamp consumes less than half the wattage of the more familiar filament lamp, many Central Station Engineers may view with misgiving the prospect of their public lighting load being seriously diminished.

Those able to look back on the introduction of the gas-filled tungsten filament lamp in place of the vacuum lamp will remember that precisely similar fears were then entertained. History as a habit of repeating itself, and history has shown that, so far from the lower current consumption of the gasfilled lamp having resulted in a reduction of revenue, the number of units sold for public lighting alone has increased from 49 million units in 1921-22, to upwards of 180 million units in 1931-32, an increase in units used of over 250 per cent.

It is, therefore, safe to predict that the OSIRA lamp will be the means, not of reducing the output of electrical energy, but of providing abdundant and "accident-proof" public lighting at a price which puts it within the reach of every district.

WOOD GREEN. A MAIN ROAD ILLUMINATED BY 400-WATT OSIRA LAMPS IN G.E.C. "WATFORD" LANTERNS. 160 SIMILAR UNITS ARE USED IN THIS AREA.

A MAIN ROAD IN DEPTFORD LIT BY 400-WATT OSIRA LAMPS AND G.E.C. "LEWISHAM" LANTERNS. OVER 100 OF THESE UNITS ARE USED IN THIS INSTALLATION.

LONDON ROAD, LEWISHAM. ILLUMINATED BY 400-WATT OSIRA LAMPS AND G.E.C. "LEWISHAM" LANTERNS. ABOUT 300 OSIRA UNITS ARE USED TO LIGHT THE MAIN THOROUGHFARES OF LEWISHAM.

WHITEGATE DRIVE, BLACKPOOL. ILLUMINATED BY 400-WATT OSIRA LAMPS AND G.E.C. "WATFORD" LANTERNS. 200 OF THESE LAMPS ARE ALREADY INSTALLED AT BLACKPOOL.