OCTOUEK 21, I909J 



jVA rURE 



.SOI 



volts, have been produced ; one company has even professed 

 to manufacture a 200-volt i6-candle-power 25-watt lamp. 



Attention may also be directed to the cooperation between 

 the lamp-makers and the electrical supply companies 

 characteristic of the United States, and to the work of the 

 National Electric Lamp Association in that country. A 

 large number of lamp-makers belong to this association, 

 determine standard prices, and support a laboratory for 

 the purpose of carrying out common tests on lamps for 

 their mutual benefit. In addition, the cooperation between 

 lamp-maker and supply company is naturally very beneficial 

 to both parties in pushing the sale of lamps in desired 

 directions. 



Electric Arc-lamps and Vapour-lamps. 



The most marked development in arc-lamps of late, 

 years has been the introduction of flame carbons, that is, 

 carbons such that the light comes from a bridge of in- 

 candescent vapour instead of the tips of the electrodes. By 

 this means consumptions so low as 0-2 watt to 03 watt per 

 mean spherical candle-power are said to have been obtained. 

 Flame carbons, however, burn away very quickly, and in 

 order to extend their life lamps in which a succession of 

 carbons is automatically used have therefore been intro- 

 duced. Another development, the enclosed regenerative 

 lamp, involves methods enabling the access of air to the 

 carbons to be restricted, so that a high efficiency, and yet 

 a fairly long life, is obtained. Mention must also be made 

 of the new Blondel flame carbons, yielding a very white 

 light, which have been stated to yield a polar curve of 

 light-distribution specially well adapted for street lighting, 

 and are burned vertically one above the other. 



Another direction of progress has been the improvement 

 of small candle-power enclosed arc-lamps, which formerly 

 served to bridge the gap between high candle-power flame 

 arcs and glow-lamps. By securing more complete e.\- 

 clusion of the air from the globe, the Regina Arc Lamp 

 Company claims to manufacture a lamp consuming only 

 0-8 watt per candle, and lasting for 250 hours without re- 

 carboning. High candle-power metallic filament incan- 

 descent lamps, which are manufactured up to 1000 candle- 

 power, now also serve to fill this gap. 



The chief drawback of mercury-vapour lamps is, of 

 course, the peculiar colour of their light, there being prac- 

 tically no red rays. It has, therefore, been proposed to 

 mix certain salts with the mercury, to use fluorescent 

 materials, &c., in order to improve the spectrum, but few 

 such devices have come to a practical issue. A recent 

 advance has, however, been achieved by Dr. Kiich, of 

 Germany, by the use of a tube composed of special quartz- 

 glass, which can stand a very high temperature. By this 

 means a consumption of only 027 watt per mean spherical 

 candle-power is said to have been obtained ; an incidental 

 advantage is that the luminescence in the tube seems to 

 be partially replaced by temperature radiation, and there- 

 fore file light contains a distinct red element, the spectrum 

 broadening out into a more or less continuous band instead 

 of consisting of isolated lines. 



In addition, quartz-glass allows ultra-violet light to pass 

 through with special ease, and the lamp is therefore 

 believed to have special uses for the destruction of bacteria, 

 photographic purposes, &-c. For ordinary illuminating pur- 

 poses a special absorbing glass envelope restricting these 

 rays Is used. The Moore tube utilises gases in a rarefied 

 condition and subjected to a high-tension alternating dis- 

 charge. The essential feature of this arrangement is the 

 use of a valve which automatically keeps the condition of 

 the gas within the tube constant. 



Gas Lighting. 



Great advances have been made in the efficiency of gas 

 burners since the early flat-flame burners yielding only 

 about 3 candle-power per cubic foot. The most recent 

 figure is furnished by the Keith high-pressure light, for 

 which 60 to 70 candles per cubic foot have been found by 

 some observers. 



Improvements have been made in the incandescent 

 mantle both in the direction of the colour of the light 

 and through durability. Even so, manufacturers in 

 England have stated that, as a rule, mantles require 

 renewing every 200 hours. 



NO. 2086, VOL. Si] 



A new departure was introduced some years ago by the- 

 Plaissetty soft mantle, and more recently the Cerofrim. 

 Company is stated to have made advances in the same 

 direction. For such mantles it is claimed that their soft- 

 ness renders them convenient for package, and that they 

 naturally burn into the shape of the flame, and are thus; 

 used under the most efificient conditions. The introduc- 

 tion of the inverted mantle has, of course, also been a 

 great advance, although only two years ago there were 

 many who doubted its commercial possibilities. 



At the same time, steady improvements in the design 

 of inverted burners have proceeded. Many tvpes on the 

 market are specially designed to avoid discoloration of the 

 fitting through heat, to secure all the conditions most 

 favourable to complete combustion. Whittaker and Litle 

 in the United States, and, more recently, Lebeis in 

 Germany, have described thermostatical methods of auto- 

 matically regulating the access of air to the burner, which 

 frequently requires adjustment, as the burner after lighting 

 gradually becomes heated. 



Perhaps the greatest advance has been in the direction 

 of high-pressure gas lighting, which serves to promote an- 

 intimate mixture of gas and air, favouring complete com- 

 bustion. To this end gas at high pressure may be used, 

 or air at high pressure led into the burner, or a mixture 

 of gas and air at high pressure. In any case, however, 

 special external arrangements are needed with an exist- 

 ing low-pressure installation. Self-contained, highly efVicient 

 lamps, which can be run off the ordinary low-pressure sup- 

 ply, have therefore been designed. For instance, the Lucas 

 lamp employs a small fan driven by an electric motor, 

 which receives current from a thermopile near the mantle. 

 In the Chipperfield lamp, a small hot-air engine placed 

 above the burner automatically pumps air under pressure 

 into the burner. 



.An Important field in gas lighting is the use of auto- 

 matic ignition devices. These may consist of electric- 

 sparking apparatus, of clock-work arranged to turn orr 

 and off the gas by means of a bye-pass at specified hours, 

 or automatic devices of the same type manipulated by a 

 rise or fall in pressure. Clock-work systems are very 

 trustworthy, but, of course, do not take account of peculiar 

 atmospheric conditions, such as fog. Apparatus of the last 

 tvpe can be controlled from the station, and lamps can be 

 lighted up or extinguished as the engineer desires. 



Mention must also be made of the special Norwlch- 

 svstem for interior lighting and of the pneumatic methods ; 

 these, too, involve the use of the pilot flame. 



The subject of street lighting formed the object of study 

 of a deputation to the Continent recently appointed bv 

 the Corporation of London, and w^as subsequently investi- 

 gated by the lecturer in a visit to Germany. A novelty 

 of considerable interest, with which experiments are 

 being made at Stuttgart, consists in slinging gas lamps 

 on wires spanning the street, just as is done in the casi» 

 of electric arc-lamps in Cannon Street at present. Lastlv. 

 in this section of the subject, the lecturer refers to th*^ 

 recognition of the importance of the heating power of gas. 

 which is now regarded as more vital than its " Illuminating- 

 nower. '* according to the prescribed tests with flame- 

 burners, for modern methods of lighting, and discusses the- 

 suggestion of a calorific standard in the future. 

 Gas, Oil, Acetylene, and other Self-contained Methods of 

 Lighting. 

 The simple method of lighting by petroleum lamps, the 

 author points out, should not be neglected. It is used, 

 for instance, in the Church of St. Sophia of Constanti- 

 nople, where it is preserved on account of Its decorative 

 value and because of religious tradition. In addition, 

 petroleum lamps are still used in the country, and give 

 good results when properlv handled ; in this connection the 

 researches of Mr. Guiselln, who has demonstrated the 

 .-idvisabillty of keeping the reservoir in oil lamps well' 

 filled, are of Interest. For instance, the Illuminating power 

 was found to be improved by 20 per cent, when 700 cubic 

 centimetres instead of 500 were retained in the reservoir. 



Recently many methods of incandescent oil lighting, that 

 is, the use of vaporised fuel with an incandescent mantle, 

 have been devised. The Kitson system and the Empire 

 light are stated to be very efficient for lighthouse work* 

 and for the illumination of large outdoor areas In remote- 



