Dr Fyfe on the Illuminating Power of Coal and Oil Gas-. STB 
illuminating power. In some cases the olefiant gas did not ex- 
ceed 3 per cent. ; consequently, when added to that which is 
first discharged, must diminish the proportional quantity in the 
whole. Could this, therefore, be thrown away, the illuminating 
power might be augmented. But the same remark applies to 
coahgas, that disengaged towards the end of the distillation al- 
so yielding very little olefiant gas. It becomes, therefore, an 
object of importance for coal-gas companies to consider whether 
they can afford to throw this away, so as to increase the value 
of the gas exposed for sale. This, I conceive, they can afford 
to do much more easily than oil-gas companies, because the ex- 
pence of the raw material is a mere trifle compared to that of 
oil ; and though, by diminishing the length of time of each 
charge, the retorts require to be more frequently filled ; yet for 
the time lost in doing this, there might be a recompense in the 
saving of the retorts themselves, and the time spent in making 
a small quantity of bad gas being occupied in getting one of su- 
perior quality. 
The experiments on the illuminating power of the gases per- 
formed with Mr Milne, lead to a very important question, 
Which is the best method of consuming them, so that the great- 
est light may be got from a certain quantity ? 
No. 1. Argand burner, with five holes, consumed 2.25 feet of 
coal-gas per hour, giving a light equal to that of 3.84 candles 
for each foot consumed. No. 2, with double the number of 
holes, consumed 3 feet, the light being equal to that of 6.6 
candles per foot. 
In another trial, the Argand No. 1. consumed 1.79 feet, 
giving for each foot a light of 4.02, whereas the consumpt of 
No. 2. was 3 feet, and the light that of 4.33 candles per foot. 
Similar results were obtained with oil-gas. 
No. 1. Argand burner, with ten holes, consumed 1 foot, 
giving a light equal to that of 6.78 candles. No. 1. (of Glas- 
gow), with the same number of holes, but having a larger cy- 
linder, consumed the same quantity, but gave a light of 7.21 
candles ; whereas the burner No. 2. with fourteen holes, con- 
sumed 1.95 feet, the light for each foot being that of 7.8 candles. 
In another trial, No. 1. consumed 1.46 feet, and gave a light 
