ARTIFICIAL ILLUMINATION. _ 165. 
mantle be carefully taken off, or even the upper part of the burner, 
including the mantle, simply removed, and the rest of the burner » 
vigorously blown through, this evil will in all probability be effectually 
cured and the light will be then as good as ever. (4) Should:a® 
burner be in any exposed place where draughts are likely to break - 
the chimney, a mica chimney should be used, which, though it absorbs ~ 
perhaps 10 per cent. more of the light than a glass chimney does, is 
practically imperishable. With these hints I do not think any one 
should experience any more difficulty in the management of the light 
than my own domestics do, who have thirteen or fourteen burners 
in daily use. 
The Welsbach light is a purer white than that given by ordinary - 
gas burners, being particularly rich im the blue rays. and therefore 
more like sunlight in its power to render truly the proper. colours of 
pigments and coloured bodies generally. This is a valuable set-off 
against the objection made to it sometimes, that it is more trying to 
the complexion than the comparatively yellow light of ordinary gas 
burners. It can, of course, be tinted or softened to any amount by the 
use of opal or coloured globes or chimneys. 
The average efficiency of a Welsbach mantle may be taken as from . 
12 to 18 candle power per cubic foot of gas per hour. Thus we may 
say that at a single stride the efficiency of gas-burning has been doubled 
by this new system as compared with the best results which. were 
previously possible, and an efficiency about six times as great as that. 
usually obtained from good ordinary open burners is now within the 
reach of everybody. 
I would like now to turn your attention to the latest novelty in ga 
lighting. You remember that when we were discussing the right and 
the wrong way of using gas for cooking, it was mentioned that if a 
burner were badly used the poisonous gas acetyline might be evolved 
from the flame. Now this acetyline gas has a virtue as well as a vice, 
for it possesses a very high intrinsic illuminating power, and lately a 
good deal of attention has been directed to its properties as an illumi- 
nant or as an enricher of ordinary coal gas by Professor Vivian Lewes 
and others. We have here a small gas holder containing this acetyline 
gas, and I am now burning it in an ordinary flat flame at a very small 
fish-tail burner which passes only about a half of a cubic foot of gas 
per hour. Acetyline is so rich in carbon that it can only be burnt, 
without smoking, at very small burners, unless a special air supply be 
provided. You observe the brilliant white light which this little jet is 
now giving us. ‘The intrinsic illuminating effect is about 48 candle 
power per cubic foot of gas burnt—an extraordinary result and we 
naturally ask the question:—Can this gas be economically used for 
practical illumination? Up to the present there seems to be little 
encouragement in this direction, because, apart from the question of 
the cost of its production on a commercial scale, which is at present a 
much debated point, the exceedingly poisonous nature of acetyline, and 
even its very richness in carbon, necessitate extremely careful handling 
of the gas and adjustment of the burner. It has been suggested that it 
might with advantage be used as an enricher of ordinary coal gas, but 
in this respect it has proved not so economical as oil gas or benzine. 
