Mr Anderson on the Illuminating Fo'mr of Coal Gas. 171 
Burners. 
No. Cubic inches 
■ consumed per 
Hour, 
No. of Candles 
giving an equal 
Light. 
No. Cubic Inches 
giving a Light 
equal to Candle. 
3 Jet, 
20T4 
6 
346 
Argand 5 holes, 
2592 
8 
324 
Do. 10 do. 
3798 
12 
3164 
Do. 14 do. 
5940 
191 
308 
Do. 18 do. 
6804 
21 
324 
The mean of these results is, that S2Si cubic inches of the 
Perth coal-gas afford a light equal to that of a candle for an 
hour. Now, according to Mr Milne’s enquiries at different oil 
gas manufactories, taken in connection with his own experi- 
ments, it appears, that a burner consuming 1 cubic foot of oil 
gas per hour, yields a light equal to that of 8 candles ; or, which 
is the same thing, 216 cubic inches of oil-gas afford, during the 
same time, a light equal to one candle. From these data, it fol- 
lows, that the volume of oil-gas, is to that of the Perth coal gas, 
giving an equal degree of light, as 216 to 323 1, or in the ratio 
of 1 to 1|. 
This conclusion, though agreeing in substance with the re- 
sults obtained by Mr Leslie and Dr Fyfe, must not be extended, 
however, to every species of coal-gas ; as it cannot be doubted 
that the quality of carburetted hydrogen, obtained from pit- 
coal, must be greatly affected, not only by the nature of the ' 
coal from which it is procured, but, in no small degree, by the 
purifying processes to which it is subjected. It is to these cir- 
cumstances, that we must ascribe the very opposite statements, 
respecting the comparative illuminating powers of oil and coal 
gas, which are now pressed upon the public attention, with an 
anxiety which betrays more, of the monopolizing jealousy ^of 
commerce, than of the spirit of a liberal and enlightened philo- 
losophy. 
To Professor Jameson. 
Perth, ) 
Dec. 15. 1824. j 
