Gas-Burners, and on the Illuminating Power of the Gases. 21 
Trans. 1820, p. 24.) We have uniformly found, however, that there is a pro- 
gressive gain according as the jet-holes are made to approach nearer and nearer 
each other. The following series of experiments with oil-gas will prove this 
progressive gain, and settle the limit at which it stops. A burner, whose 
circle of holes was T %ths of an inch in diameter, being the size of No. 2. of the 
Edinburgh Oil-Gas Company, was drilled with 8, 10, 15, 20, and 25 holes, 
a 50th of an inch in diameter ; and in each the gas was burnt with the most 
favourable height of flame. The following were the results in relation to the 
light and expenditure of a 4-inch jet, taken each at 100. 
VIII. 
X. 
XV. 
XX. 
XXV. 
Light, 
360 
360 
391 
409 
382 
Expenditure, 
367 
318 
296 
289 
275 
from which the following proportions may be obtained for equal expenditures, 
that of the jet being 100, 
98 113 132 141 139 
Hence it appears, that no advantage is gained by combining the jets in an Ar~ 
gand burner of the size mentioned above, if the holes are only eight in num- 
ber ; and that the gain does not increase after the number amounts to 20. 
Results of the same nature were obtained with other oil-gas burners of various 
sizes. 
The most advantageous distance, therefore, for jet-holes a 50th of an inch 
in diameter, is T §~ths of an inch. We have remarked, that, at this distance, 
however low the flame be made, even so as to be barely visible, the jets are 
united into a uniform ring. Perhaps this rule may be adopted for the con- 
struction of all sorts of burners. It is necessary to observe, however, that, 
for a great public company, burners with the distance so small are liable to a 
material inconvenience, which we shall mention when we treat of the influ- 
ence of the glass-chimney on the light. On account of that inconvenience, 
we should recommend a distance of -f^ths for public companies. The burner 
used in the preceding series of experiments would then have fifteen holes. 
The cause of the superiority of Argand burners over jets, is to be sought 
for in the same principle, which has been already applied to explain the in- 
fluence”of the length of flame, and of the diameter of jet-holes. Mr Brande has 
followed the generally-received idea, that “ it is owing to the combustion be- 
ing perfected in the Argand burner by the central current of air, rendered 
more rapid by the glass-tube which surrounds the flame,” {Phil. Trans. 1820, 
p. 22.) We have shewn, however, that the ratio of the light to the expendi- 
ture is by no means always increased by such means ; and, on the whole, a cor- 
rector explanation will be, that the flames, being completely united from the 
bottom, a less proportional surface is exposed to the action of the air, less air, 
too, is mingled with the gas at its exit, and consequently less of the gas is, 
burnt without previous decomposition. 
Any one may remark, on examining a good Argand burner, that the base 
of blue light, which, we have said, arises from the gas being burnt at once in 
the state of gas, is proportionally much shorter than in a jet; and that the 
body of the flame has no blue margin like the jet-flame* The difference is 
still more obvious on comparing together a good Argand burner with one of 
