Gas-Burners , and on the Illuminating Power of the Gases. 19 
tainly, with coal-gas, as now made here, the diameter cannot be advantageously 
made less than a 28th part of an inch. As to oil-gas, we have found, that, when 
the specific gravity is 944, the proportional light given out by 3-inch flames 
from jet-holes of a 60th, 50th, and 45th, was, for equal expenditure, 85, 97 , 
and 100. It is probable, therefore, that for good oil-gas, varying in specific 
gravity from 900 to 1000, the best diameter for the hole of a jet-burner is a 
45th. Jet-holes, so small as a 60th, are not only uneconomical, but have also the 
additional disadvantage, that their flame is easily blown out. 
The single jet-burners of the London Portable Gas-Company, of which a 
branch has been lately established here, are constructed differently from those 
now mentioned. The aperture is in the centre of a little circular plane, about 
a sixth of an inch in diameter, and six shallow grooves are cut in the plane, 
proceeding like radii from the aperture to the edge. The flame of this jet is 
much broader than that of the common jet-burner ; when inches high, it is 
apt to flicker like that of a candle ; it is obviously more dusky and yellow than 
a 3-inch flame in a jet of ordinary construction ; and, altogther, it is very like 
the flame of a tallow-candle. It cannot be raised above 2| inches without be- 
coming brown at top, and then gives about half the light of a 4-inch flame in 
a common jet. For equal expenditures, the latter gives 9 per cent, more 
light than the former. We question, therefore, whether this new burner is 
any improvement on the old construction. 
As to the diameter of the jet-holes for Argand burners, our experiments 
shew, that it must decrease as the quality of the gas improves, and as the 
holes are multiplied. The diameter which has appeared to answer best for 
coal-gas, about 600 in specific gravity, and when the holes are ten on a 
circle of T 3 5 ths radius, has appeared to us to be about a 32d of an inch. This 
is the drill used at present in Edinburgh and Glasgow. The proper diameter 
for oil-gas will depend very much on the average we choose to assume for its 
quality. When the number of holes on a circle of T 3 5 ths radius is 15, which 
we shall afterwards shew to be the most appropriate, the diameter for gas, va- 
rying betwixt 900 and 1000, should be a 50th. When the specific gravity was 
680, the most economical diameter was about a 40th ; for if the diameter was in- 
creased to a 30th, there was a loss of 6 per cent, of the light ; if it was dimi- 
nished to a 59th, the loss amounted to 18 per cent. ; and when the diameter 
was only a 60th, the loss was 39 per cent. When the specific gravity was 776, 
nearly the same quantity of light was given with diameters of a 40th and a 50th ; 
but with a 30th for the diameter, there was a loss of 11 per cent % and with a 
60th the loss was 20 per cent. Hence, for such gas, the proper diameter would 
be about a 45th. We are therefore justified in assuming a 50lh as the pro- 
per diameter of the jet-holes of Argand burners, for gas varying in specific 
gravity from 900 to 1000. The foregoing data likewise shew, that much less 
injury is done by making the apertures somewhat larger, than by making 
them narrower than they ought to be. The diameter now assigned differs 
from that generally recommended elsewhere. The burners used in this city 
before the Oil-Gas Company commenced their operations, had their holes 
drilled to the diameter of a 40th. This is too wide for good gas. On the 
other hand, in the burners of Taylor and Martineau it is about a 6,9th; and 
in some of those used in Dublin, it is almost so small as a 70th. In both of 
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