, ON THE COMBUSTION OF GAS FOE ECONOJIlC PURPOSES. 
o A 
oUo 
than a rich gas ; an^ by using a jet with an aperture 0-04 of an inch in diameter, and a 
pressure of 0 5, the flame of fourteen-candle gas will be just G inches in height. 
The fourth method for determining the quality of gas is by ascertaining the quantity 
of air necessary to destroy its light. The best instrument for determining it is the appa¬ 
ratus designed by M. Erdmann, and which is called agas-prover. It is a sort of Bunsen 
burner, with.a contrivance for graduating the supply of air. Erdmann recommends the 
gas to be turned on until there is a flame of a given height, and then the supply of air 
is admitted until the light is destroyed. This, however, is not the proper way to use the 
instrument. The gas should first be turned on at a given rate—viz. at the rate 0'84 of 
a cubic foot per hour—and then the quantity of air necessary to destroy the light should 
be read off. In this way reliable results may be obtained, for the richer the gas the more 
air is required. 
I referred in my last lecture to this diagram, which has been prepared from the expe¬ 
riments of Mr. King, of Liverpool:— 
lUaminating Power of Gas, as estimated hy Erdmanris Gas-Prover, the Gas ourning at 
the rate o/0'84 Cubic Feet per Hour. 
Height of flame (inches) . . 
Number of index prover . . . 
Relative value of do. 
Coefficient of power .... 
Ilium, power (coefficient =0'7) 
Do. do. by photometer . 
Relative values. 
Description of Gas. 
Eqiial Parts 
Newcastle 
N ewcastle 
AVigan 
Boghead 
Coal. 
and AViffan. 
Coal. 
Coal. 
1 87 . 
2-00 . 
2-75 . 
5-50 
14-72 . 
23-39 . 
32-78 . 
G1T4 
1-00 . 
1-59 . 
2-22 
4-15 
0-70 . 
0-70 . 
0-72 ." 
0-70 
10-30 . 
lG-37 . 
22-93 . 
42-80 
10-30 
lG-35 . 
23-55 . 
42-9G 
1-00 . 
1-58 . 
2-29 . 
4-17 
Lastly, the common method for ascertaining the illuminating power of gas is by com¬ 
paring it with a standard flame. 
In this country, the standard was formerly a vrax candle burning at the rate of 120 
grains per hour, but the variations in the value of the light were so great, that it was 
abandoned; for, as a wax candle requires snuffing, it was difficult to decide when it was 
burning in a proper manner. After numerous experiments, extending over a year, I 
ascertained that, for equal consumptions, the light of wax and sperm was as 14 to IG— 
in other words, the power of sperm was just one-seventh greater than that of wax. 
At present, the standard flame in this country is a sperm candle of six to the pound, 
burning at the rate of 120 grains per hour. But for some time past this standard has 
also become uncertain—first, because there has been great irregularity in the construc¬ 
tion of the wicks ; and, secondly, because the sperm is being adulterated Avith Avax and 
parafiin or both. The irregularity of the Avick causes a variation in the rate of burning 
from IIG grains .per hour to 140 ; and the real walue of the light in the two cases, when 
reduced to the standard consumption of 120 grains per hour, if as 9G to IIG. The 
adulteration of the sperm Avith wax and paraffin also affects the A-alue of the light, for 
the former gives 13 per cent, less light than sperm, and the latter gAes 23 per cent, 
more light. These irregularities are becoming so serious, that we must ere long change 
the standard. 
In France, the standard is a Carccl lamp of specified dimensions in every particular, 
burning refined colza oil at the average rate of G48 grains per hour. With proper pre¬ 
cautions this standard appears to be very uniform, care being taken that the consump¬ 
tion of the oil is never less than GI7 grains per hour or more than G79. 
And now, in concluding this part of the subject, I Avill direct your attention to the 
comparative power and value of the most important illuminating agents. 
Relative Value of different Illuminating Agents. 
Name, 
(lannel gas 
Coal gas . 
Benzole . 
Rate of Consump. Ilium. Power, 
per hour. (Sj^erm 120.) 
4 feet . . 18'G7 . 
5 ,, , . 14'00 
301 grs, . 4-91 . . 
Quantity = 
11 Candies. 
3 feet. 
857 grs. 
