ON TEE DEVELOPMENT OF LIGHT FROM COAL-GAS. 



117 



nected by a vase of brass. Only the three smallest sizes of these are 

 suitable for rich cannel-gas, the larger ones being intended for^ gas of 

 lower quality. The following are the results obtained with 26 candle 



Several varieties of regulating batwings have been invented by Sugg, 

 Witthoft, Winsor, and others ; the principle of their construction being 

 to check the flow of gas by means of a plug regulated by a screw. At a 

 given pressure in the pipes the burners may be regulated to deliver any 

 desired quantity of gas ; and in the experiments on the Winsor and Sugg 

 burners quoted below, they were regulated so as to burn the number of 

 cubic feet per hour corresponding with the numbers marked on the 

 burners. Gas used = 26 candles : — 



If two batwing flames are brought together, especially if the slits be 

 narrow, the gas of low quality, and the pressure somewhat high, the 

 illuminating power of the united flame is greatly in excess of the sum of 

 the two tested separately. Upon this principle is constructed a double- 

 slit batwing, the slits being about 1 millimetre apart, which is used in 



