Gas-Burners, and on the Illuminating Power of the Gases. && 
oil-gas flame. Taking the mean relative expenditure 212 to 311, the propor- 
tional light by this method is 100 to 233. The proportion obtained by Pro- 
fessor Leslie ( Coal-Gas Company's Report , 10th July 1824,) is only 100 to 150 * *. 
As he has not given all the particulars of his experiments, it is impossible to 
say precisely what is the cause of this low result. W e have found, however, that 
the burner he used in the first comparative experiment, while it is a very ex- 
cellent burner for coal-gas, burns good oil-gas at a loss of 13 per cent, of the 
light, farther, Mr Leslie mentions, that he procured oil-gas of three diffe- 
rent specific gravities, 674, 810, and 943; but he omits to state distinctly 
which of them he used in the experiments he publishes. Now, in the afore- 
said burner, the expenditure with his gas was a foot in 33 minutes ; while we 
find that, when the specific gravity is 910, the expenditure with that burner 
does not exceed a foot in 46 minutes. Nay, this is only when the flame is 
nearly 3 inches tall, which is an elevation considerably greater than that univer- 
sally employed here at the time Mr Leslie made his experiments, and therefore 
probably greater than he would think of using. Hence, the gas he employed 
must have been of low specific gravity ; most likely, indeed, it was that speci- 
men which had a specific gravity of 810. If we correct these probable errors, 
the proportional illuminating power becomes, instead of 2 to 3, 15 to 29.7* 
Again, if he really used an oil-gas of this low specific gravity, as appears to us 
very likely, he must have found, that, with a gas of average quality, such as 
* The instrument we used was that of the Astronomical Institution. As 
the Report referred to in the text cannot now be easily procured, the follow- 
ing extracts are reprinted from it : 
“ A small quantity of oil-gas, procured for the experiments, I found to 
have the specific gravity of only 674, not greater indeed than that of your 
coal-gas, when made from the best coal. The oil-gas, however, furnished by 
Mr Mylne, manufactured on a small scale, and apparently with great care, at 
his works, was materially denser, being as high as 943, though on a former 
occasion I found it to be only 810.” 
* * * * s * 
u The illuminating powers of the two gases were measured with great accuracy, 
by the application of my photometer, which I had somewhat modified, to ex- 
clude every irregular influence of heat. The indications were steady and easily 
noted, nor could the judgment of the observer be liable, as in other cases, to 
any sort of bias or indecision. It hence appears to be ascertained, that, with 
the same burner, the powers of illumination of different gases, and of the same 
gas in different states, are very nearly proportional to their densities. The 
same weight of gas of any kind gives out the same quantity of light ; but if 
equal bulks be taken, the illuminating powers follow the ratio of their densi- 
ties. But the quantity of light emitted is not uniformly proportional to the 
measure of the gas expended. A certain burner, for instance, was observed to 
produce double the illuminating effect, though it consumed only one-half more 
of either species of gas. With No. 1. of the oil-gas burner, the relative illumi- 
nating power of Mr Mylne’s oil-gas to that of your coal-gas, was found to be as 
6 to 5. But a cubic foot of the former lasted 38 minutes, while a cubic foot of 
the coal-gas was spent in 30 1 minutes. The relative volumes consumed were, 
hence, in the space of an hour, 1.58 and 1.97, or in the ratio of 4 to 5, Where- 
fore, while 5 cubic feet of coal-gas give 5 degrees of light, 4 cubic feet of the best 
oil-gas give 6 degrees ; that is, for equal volumes, the illuminating power of the 
oil to the coal gas is as 3 to 2. The same conclusion was obtained on passing 
those several gases successively through the Argand coal-gas burner, No. 2.” 
u Thus the illumination of oil-gas is actually less than one-half of what 
has been currently asserted,” 
VOL. XIII. NO. 25. JULY 1825 . 
c 
