324 NOTICES OF THE MEETINGS [May 20, 
that of lamps or candles, and consequently, when three or four 
times the amount of light is produced from a gas of bad composi- 
tion, the heat and atmospheric deterioration, greatly exceed the 
corresponding effects produced by the other means of illumina- 
tion. By using a gas however of nearly the normal composition, 
such as the hydrocarbon gases above named, it is evident that 
three or four times the light may be employed, with the pro- 
duction of no greater heat or atmospheric deterioration, than that 
caused by wax candles or the best constructed oil lamps. 
But there is nevertheless a real objection to the employment of 
gas-light in apartments, founded upon the production of sulphurous 
acid during its combustion: this sulphurous acid is derived from 
bisulphuret of carbon, and the organic sulphur compounds, which 
have already been referred to as incapable of removal from the gas 
by the present methods of purification. 
The formation of sulphurous acid can readily be proved and even 
its amount estimated, by passing the products of combustion of a 
jet of gas through a small Liebig’s condenser; the condensed 
product being heated to boiling with the addition of a few drops of 
nitric acid, and then treated with solution of chloride of barium, 
yields a white precipitate of sulphate of barytes, if any sulphur com- 
pound be present in the gas. 
These impurities, which are encountered in almost all coal gas 
now used, are the principal if not the only source of the unpleasant 
symptoms experienced by many sensitive persons, in rooms lighted 
with gas. It is also owing to the sulpburous acid generated during 
the combustion of these impurities, that the use of gas is found to 
injure the bindings of books, and impair or destroy the delicate 
colours of tapestry. Therefore the production of gas free from these 
noxious sulphur compounds is at the present moment a problem of 
the highest importance to the gas manufacturer, and one which de- 
mands his earnest attention. ? 
As it is nearly impossible for the consumer to procure gas free 
from these objectionable compounds, the only method of obviating 
their unpleasant and noxious effects is to remove entirely the products 
of combustion from the apartments in which the gas is consumed, 
and thus prevent them from mingling with the circumambient air. 
This suggestion was first made by Faraday, who, for accomplishing 
this object, contrived the very beautiful and effective ventilating 
burner exhibited in operation upon the lecture table. This apparatus, 
which is used at Buckingham Palace, Windsor Castle, the House of 
Peers, and in many public buildings, may be truly said to have brought 
gas illumination to perfection; for not only are all the products 
of combustion conveyed at once into the open air, but nearly the 
whole of the heat is in like manner prevented from communicating 
itself to the atmosphere of the room. ‘The only obstacles to the uni- 
versal adoption of this description of burner are its expense, and 
the difficulty of conveying the ventilating tube safely into the nearest 
