ON THE DEVELOPMENT OF LIGHT FROM COAL-GAS. 



253 



adapted is used, that the liiglier illuminating power results are obtained. 

 With smaller amounts the loss of light by the excessive supply of air 

 which then enters the chimney is much greater than in the case of flat- 

 flame burners of good quality. On burning various quantities of gas 

 through the standard Argand used for testing, the following results were 

 obtained : — 



By reducing the consumption of gas from 5 feet to 2-5 feet per hour, 

 the illuminating power is reduced from 16 candles to S'O candles per 5 

 cubic feet. 



The amount of light lost for illuminating purposes by the use of globes 

 around the lights has been mentioned in the first part of this Report. In 

 many cases this loss is considerable, and the use of globes with narrow 

 openings, and made of very opaque white glass, should be avoided. 

 The principal advantage of the use of globes is that the direct glare of the 

 flames is prevented, and the light is softened and diffused in a pleasant 

 manner. It is often worth the sacrifice of a portion of the light to produce 

 this effect. With properly made globes of thin milk-white glass, having 

 openings of not less than four inches at the bottom, and still wider ones 

 at the top, the loss of light can be to a great extent avoided, the light 

 being reflected by the white surfaces of the interior of the globe through 

 the wide openings both upwards and downwards. 



From what has been frequently shown in this report it will be seen 

 how very important it is to have complete control of the pressure at which 

 the gas is supplied to the burners in order to develop its light-giving pro- 

 perties to the best advantage. The first part of the report jjoints out the 

 various causes which give rise to great fluctuations of the pressure in the 

 gas mains. In many towns the pressure may vary from less than an inch 

 to four inches. No doubt the pressure as supplied to the burners can be 

 regulated by the taps at the burners or at the meter, but in many situa- 

 tions where the pressure alters much in the course of a single night this 

 is very troublesome to attend to, and in most cases will be neglected. It 

 is best in such places to have governors which act automatically by the 

 pressure of the gas. 



Besides the various governors already mentioned suitable for a number 

 of lights, it is now possible to obtain governors suitable to be applied to 

 single lights at a cost within the reach of most gas consumers. These 

 are placed near the burner, and in many cases form a part of the burner. 

 In many situations subject to great variations of pressure it is worth while 

 on the score of economy to adopt such burners. Vastly different amounts 



