ON THE DEVELOPMENT OF LIGHT FROM COAL-GAS. 



115 



The following table gives the results of tests of a series of steatite 

 batwing burners manufactured in Germany — gas 26 candles: — 



The considerable loss of light experienced when gas is consumed in 

 batwing burners at any but comparatively low pressures has given rise 

 to many efforts to combine with the jet an apparatus to reduce the pres- 

 sure of the gas before it issues from the narrow slit. Various burners 

 having obstructions have been constructed, of which Bronner's is one of 

 the best known. It consists of a somewhat pear-shaped brass body, with 

 a steatite top similar to those of which the results are given above, and at 

 the bottom a small piece of steatite in which is an oblong slit. There 

 are, for cannel-gas, six sizes of bodies, the sizes depending upon the area 

 of the slits ; and five sizes of tops, and as these screw into one another, . 

 there are thirty possible combinations. In none of these combinations, 

 does the pressure of the gas at the point of ignition exceed - 5 of an 

 inch with an initial pressure of 1'5 inch, while in some it is only j2, and 

 in some it is so low that the flame smokes and is useless. The rate of 

 combustion is dependent on these conditions — 1st, the area of the opening 

 at the bottom ; 2nd, the area of the slit of the burner ; and 3rd, the 

 initial pressure of the gas. The range of combinations enables one to 

 select a burner to suit almost any description of gas or any standard of 

 pressure. The accompanying table gives the results of tests at i inch 

 and 1-5 inch, with 26 candles; the burners are not adapted for lower 

 pressures than 1 inch. 



For common gas (i.e., of 14 to 16 candles) a different series of tops 

 is provided, in which the areas are considerably greater than in those 

 made for cannel-gas, and in which the pressure is reduced to from -1 to 

 •3 of an inch. These burners cannot be used with cannel-gas, although 

 with common gas they are exceedingly effective and are much in use, 

 especially in London : — 



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