GAS AND GAS METERS. 



ISI 



flow of gas along the line will vary from hour to hour, consequently the 

 pressure at his house may be expected to vary from hour to hour. 



The unit of measurement of gas pressure is that pressure which 

 will cause a difference of water level of one tenth of an inch in the 

 two legs of a V-shaped tube when one end is connected with the gas 

 main and the other end is left open to the outer air. Ten tenths, or 

 one inch, is the standard, or normal pressure. 



Any appliance — even a gas-burner — operates to best advantage 



under certain well-defined conditions. Depart from these conditions, 

 and the efficiencv of the device is impaired to an extent depending 

 largely upon the nature of the appliance under consideration. For 

 exam i»le, burn an incandescent lamp at fifty per cent, above normal 

 voltage and it breaks down; burn a gas jet at two hundred per cent, 

 above normal pressure, and it still operates — how satisfactorily 'de- 

 ponent sayeth not.' Now, the gas-burner is supposed to operate to best 

 advantage at ten tenths of an inch. At this pressure the flame is neither 

 so wavering as to be affected by every chance draught, nor so rigid as to 



