i 4 SCIENCE PROGRESS 



The Moore vapour lamp is a direct application of the 

 vacuum tube discharge to electric lighting : long glass tubes 

 are used, running for example entirely around the cornice of a 

 room ; these are filled with air or other gas at a very low 

 pressure : a discharge at high voltage, 10,000 volts or over, is 

 passed through this tube. The colour of the light, which de- 

 pends on the particular gas with which the tube is filled, is 

 good but the consumption is as high as i*8 watts per candle 

 and the cumbrous construction of the lamp hinders its general 

 utility. In many ways an ideal form of lighting, notably in the 

 admirable distribution of the light and the low intrinsic brilliancy 

 of the source, the low efficiency and other drawbacks must 

 prevent the Moore lamp competing with much success against 

 either the tungsten or flame lamp. None of these lamps can 

 yet be regarded as real competitors in the field of artificial 

 lighting and until they have been improved sufficiently to 

 qualify them in this way their more detailed consideration may 

 be deferred. 



From what has been written it will be seen that during the 

 last five years a remarkable development of electric lamps has 

 taken place which may confidently be expected to involve a 

 no less remarkable development in electric lighting. It may 

 even now be difficult for electric lighting to compete with gas 

 lighting but this is due to the high cost of producing and 

 distributing electric energy and not to the inefficiency of the 

 means of converting it into light ; though the result may be 

 low absolutely it is relatively remarkably high. Even when the 

 best that he could produce was represented by the carbon 

 filament lamp and the open arc, the electrical engineer could 

 boast that he had devised the most efficient light-producing 

 apparatus to be found : the developments of the last few years 

 appear to render this position unassailable. Nevertheless, 

 there is ample room for improvement : the most efficient of the 

 electric lamps consumes as much as o'4 watt per candle. 

 Could electric energy be converted directly into light without 

 any waste as heat, the consumption would be only 0*08 watt 

 per candle. Great, therefore, as the progress has been in the 

 last five years, there is open to the investigator a field for 

 greater progress still. 



