244 



REPOllT — 1880. 



issuing from No. 2 batwing under a pressure of 1-5 inches is compared 

 with the result of burning tlie amounts of gas nearest to this amount in 

 the case of each of the other burners, it will be seen that the illuminating 

 power increases as the pressure required to send the desired amount of 

 gas through the burner decreases ; or, in other words, the illuminating 

 power is increased as the gas, issuing with less velocity, is thus mixed or 

 brought into contact with less air. The following figures taken from the 

 above table show this : — 



It will also be observed, in examining the above tables, that in the 

 case of each burner there is a certain consumption and a certain pressure 

 which gives the best result, and that at all other consumptions and 

 pressures above or below this the results are worse. No. 6 union-jet, for 

 instance, gives the best result when consuming 38 cubic feet of gas under 

 0'5 inch pressure ; No. 2 batwing gives the best result when consuming 2-8 

 cubic feet under 07 inch pressure ; No. 6 batwing the best result when 

 using 47 feet of gas under a pressure of 07 inch, and the large batwing, 

 when using 3 cubic feet of gas under a pressure of 12 inches. There 

 is, therefore, a limit to the reduction of pressure, causing an increase of 

 the illuminating power of the gas consumed, and this limit is reached 

 when the flame ceases to have a somewhat definite form, and burns in a 

 languid, waving manner, showing very low intensity of combustion, and 

 having a tendency to smoke. In such cases the air is not supplied suffi- 

 ciently for vigorous and intense combustion. This condition is illustrated 

 in the above tables, and especially in the case of the batwing burners. 

 With each of these buimers the gas issuing under the lowest pressures 

 ■used produced less light than when higher pressures were used. Thus, 

 for instance. No. 6 burner gives a light equal to only 9-3 candles per 5 

 cubic feet when the gas issues under a pressure of OS inch, which is 

 increased to 13-5 candles per 5 cubic feet when the pressure is increased 

 to 07 inch. Again, with the large batwing having a slit 0'020 inch 

 wide, the gas issuing at a pressure of 0*4 inch gives light equal to 14-2 

 candles per 5 cubic feet, whilst under a pressure of 1-2 inches the gas 

 yields a light equal to 166 candles per 5 feet, a result even better than 

 the standard testing burner gives. 



Another point to be noticed in the above tables is, that as larger 

 burners are used, and larger quantities of gas burned, the illuminating 

 power per 5 cubic feet is increased. Although the chief cause of this 

 impi'ovement is the better apportionment of the gas supply to the air as 

 regulated by the pressure, yet the increased volume of flame causing 

 greater intensity of combustion, and preventing the cooling of the flame 

 by the surrounding atmosphere, is doubtless another cause producing this 

 improved result. 



It has often been asserted that if gas be heated before it is burned, 



