368 Dr Fyfe on the Illuminating power of Coal and Oil Gas . 
Making their illuminating power as 17 to 32, i. e. as 1 to 1.8. 
The illuminating power of the above gases was tried by burn- 
ing them with a jet burner, so as to make them give out the 
same intensity of light ; and the quantity consumed was in a 
certain time as 1.9 coal gas to 1 oil. gas, making it 1 to 1.9. 
Exp. 2. — Gas prepared at the Coal-Gas Works, contained 
14 per cent, olefiant. 
Oil-gas prepared by myself contained 26 per cent., making 
the illuminating power as 14 to 26, i. e. as 1 to 1.8. Tried by 
the consumption it was as 1 to 1.6. 
The above experiments were performed on a small scale, in 
my Laboratory. The following, still more satisfactory, were con- 
ducted at the Coal-Gas Works, along with Mr Watson, Ma- 
nager, and Mr Kirkham, Engineer. 
The retorts were charged with 21 cwt. of the best parrot- 
coal at half an hour after eleven. 
At a quarter before twelve the gas yielded 14 per cent, of ole- 
fiant, and with a single jet burner and 3 inch flame, consumed 
0 656 of foot per hour. 
At a quarter before one, it contained 19 olefiant, and the 
burner consumed 052 of foot. 
At a quarter before two the olefiant was 17, and the con- 
sumpt per hour 0-62 of foot. 
At a quarter before three it afforded 14 olefiant, and consumpt 
was 0 64. 
At a quarter before four the gas was coming off very slowly, 
and contained only 5 olefiant, the burner consuming 0 88 of 
foot per hour. The illuminating power of this last gas with 5 of 
olefiant, was tried with another, in which there was 18 per cent. 
For this purpose they were passed through accurately adjusted 
meters, and burned with a single jet-burner. Having brought 
the intensity of shadow from both to be the same, the quantity 
consumed in a certain time was, as 7 of the former to two of the 
latter, making the power of giving light as 1 to 3*5. The ole- 
fiant gas was as 5 to 18, making it by this test as 1 to 3*6 ; so 
that by this experiment, conducted with every degree of care, 
there is only 0*1 of difference in the results by the two methods. 
The results obtained by experiments performed along with 
Mr Milne, were the same, and in these the illuminating power 
of the gases was tried under a variety of circumstances. Taking 
