ON THE DEVELOPMENT OF LIGHT FROM COAL-GAS. 



119 



barn the gas, thus avoiding the diminution of light which results from a 

 too rapid combustion of the gas, and the cooling effect of a large quantity 

 of air. The pressure of the gas inside the steatite top is considerably less 

 than -1 of an inch, and that required to pass 5 feet per hour through the 

 complete burner is about -2 of an inch. 



In the burner introduced by Mr. A. M. Silber, the steatite top with 

 wide holes (about 1 millimetre or -04 inch) is also adopted, but the body 

 of the burner is considerably prolonged, and the so-called "cone" is long 

 and cylindrical with a curved top. A very essential feature in the Silber 

 Argand is an air tube introduced into the centre of the jet, which is said 

 to carry a portion of the air to the upper part of the name, and which 

 certainly has a remarkable effect in steadying it. The funnel is 7 or 8 

 x If inches, and in consequence of the form of the " cone " is kept so cool 

 at the bottom that it may be handled without difficulty while the flame is 

 burning. Funnels of 10 inches high are also used, but while the con- 

 sumption of gas is thereby increased, the illuminating power per cubic 

 foot of gas remains almost quite constant. Mr. Silber has recently dis- 

 covered the remarkable fact that a globe or vase placed below his Argand 

 increases the illuminating power considerably ; and his statement has been 

 verified both as to common and cannel gas, the increase with the former 

 being about a candle, and with the latter about 1| candle. The effect of 

 placing a vase below an ordinary union jet was also tried, but no increase 

 of light was obtained, while the flame showed a distinct tendency to 

 "blow." That the flame of the Argand should have its illuminating- 

 power increased 6 per cent, by passing the gas through a glass vase (or 

 •cylindrical metal bos, which answers the purpose equally well) is a phe- 

 nomenon which appears to be at present incapable of explanation. 



The following table gives the results of photometric tests of various 

 Argand burners with cannel-gas of 26 candles illuminating power. From 

 3 to 4 cubic feet of gas per hour was burned in each case, and the result 

 calculated to the usual standard of 5 feet per hour: — 



German porcelain Argand, with cone (40 small holes) ... 



Leoni 40-hole burner, '-'adanias" top, with cone 



Sugg-Letheby, 15 holes, in steatite ring, perforated gallery 

 American regulating Argand, brass, 40 very large holes ... 

 Sugg's London Argand, 24 holes, with cone and regulator 

 Silber 40-hole burner, steatite top, cone, and centre tube... 



Do. 32 do. do. do. do. ... 



Do. 24 do. do. do. do. ... 



Do. do. do. with glass vase below 



Size of 

 Funnel 



7 

 7 



If 



2 

 2 



If 



8df 

 Do. 

 Do. 

 Do. 



Illumi- 

 nating 

 Power 



17-80 

 18-18 

 18-86 

 21-03 

 22-40 

 22-54 

 23-08 

 24-04 

 25-61 



The following tests were made with various Argands in order to test 

 the effect produced by the cone and by the centre tube of the Silber 

 burner : — 



