25 



ordinary maimer, the air supplied to it being cold, it t'uniished a light 

 equal to that of 21-7 candles with the same consumption of gas. 



The selection of the proper kind of burner is a matter of 

 importance. In the ordinary "fish-tail," which is so universally 

 employed, the gas issues from two circular orifices slightly inclined 

 to each other, but if the orifices be not properly inclined, or if, as is 

 commonly the case, they are obstructed by dirt or rust, the bm-ner 

 loses greatly in effectiveness. On this account, the " sht " burners 

 are to be preferred. The so-called Argand burner is a far more 

 perfect instrument than any of the flat-flame bvirners, but is much 

 less frequently adopted on account of its cost and the trouble 

 involved in cleaning the indispensable chimney ; this burner is far 

 superior to all others, as, by means of the chimney, a regulated 

 supply of air for the combustion of the gas is secured. 



More important, however, at least from an economical point of 

 view, than the form of the burner is the regulation of the pressure 

 under which the gas is burnt. The pressure of the gas in the mains 

 varies considerably, being about balanced during the day time by a 

 column of water one-half or three-quarters of an inch high, and 

 during the busy time in the evening by a column about two-and-a- 

 half to three inches high. As the pressure increases, the consumption 

 of gas also increases, but the light doe.^ not increase in the same pro- 

 portion. In illustration of this. Dr. Armstrong quoted a series of 

 experiments with a burner consuming :>ft. of gas per hour under a 

 pressure of eight-tenths of an inch of water, and giving a light equal 

 to h-ih candles ; the pressure being increased to one and seven-tenths 

 of an inch, the consumption increased to 8ft. per hour, and the light 

 emitted to y-13 candles; on further increasing the pressure to one 

 and eight-tenths of an inch, the consumption increased to 8-4ft., 

 but the Ught emitted was only equal to that of 8-9 candles ; and under 

 a pressure of two inches of water, the consumption being 8-'Jft. per 

 hour, the light emitted was equal only to 6-43 candles, being no 

 more' than that obtained by the consumption of 5-8ft. under a 

 pressure of one inch. To obtain the maximum light from gas, it is, 

 in fact, essential to burn the gas at a moderate and even rate, and 

 consequently at a moderate and uniform pressure. The Lecturer 



