Section 321. Standard of illuminating power

The maximum illuminating power
  required and minimum illuminating power permitted of gas so furnished or
  supplied in any such city shall be as follows: If a  coal  gas,  sixteen
  candles;  if  a  mixed  coal  and  water gas, eighteen candles; and if a
  carburetted water gas, twenty candles.  A  candle  shall  mean  a  sperm
  candle,  six  to  a pound, burning at the rate of one hundred and twenty
  grains of spermaceti per hour. The test for illuminating power shall  be
  made with gas obtained from a service pipe or main located at a distance
  of  not less than one mile nor more than one and one-half miles from any
  distributing holder, using, for coal gas and mixed coal  and  water  gas
  containing  more  than  fifty per centum of coal gas an F Argand burner,
  and for mixed coal and water gas containing fifty per centum and less of
  coal gas and for carburetted water gas a number seven  slit  union  Bray
  burner, on a basis of consumption of five cubic feet of gas per hour.