1816.) Scientific Intelligence. 237 
slightly warmed, a brisk effervescence ensues. To what is this’ 
effect to be ascribed ? 
I beg to know what would be the probable result if a fire were to 
destroy one of the large gasometers belonging to the Gas Light 
Company when full of gas. Would not the consequence prove 
almost as destructive to the neighbourhood as if a large quantity of 
gunpowder were to be exploded ? 
Can the gas light be safely adopted by a silversmith ?. Would not 
the sulphureous smell, which was the objection to its continuance at 
the Theatre, be likely to produce a discoloration of his silver 
articles ? 
London, Jan, 13, 1816. INQUISITOR. 
‘To the first of these queries I am unable to give any answer, as 1 
have had no opportunity of witnessing the fact. Perhaps some of 
my readers may be able to give a satisfactory explanation of it. 
Carbureted hydrogen gas possesses no resemblance to gunpowder, 
as it will not burn at all unless mixed with more than six times its 
bulk of common air. A gasometer filled with the gas, if set on fire, 
would not explode ; but the flame would probably be so violent that 
it would set fire to the house in which it was placed. 
If coal gas containing sulphur be mixed with the air of a room 
unburnt, it would doubtless tarnish silver. But it would not pro- 
duce this effect if it were burnt. I think the burners might be so 
contrived, by placing the stop-cock near their mouth, that the 
whole gas shall be consumed. In that case there would be no smell, 
nor would any injury be sustained by silver. 
VIII. Queries respecting the Mode of Cutting Glass. 
(To Dr. Thomson.) 
SIR, 
In Dr. Henry’s Elements of Chemistry, we find directions fer 
cutting off phial bottles, by winding a thread or string round them 
previously dipped in oil of turpentine, and then inflaming it. Fol- 
lowing these instructions, we have never been able to succeed. As 
a good process for cutting down oil flasks, to make evaporating 
dishes, would be extremely convenient, perhaps you will oblige us 
by communicating a successful method. 
Jan. G. K. and M. 
Answer.—I have never myself tried the method alluded to in 
this letter. My process is this. I take a bar of iron (a poker, for 
example), and heat its extremity red-hot in the fire. I then take 
advantage of any crack which previously exists in the retort or flask 
to be cut; or if no crack exists, I make one by heating a portion of 
the edge pretty hot by means of the iron bar, and then touching it 
with a drop of water. his crack is readily extended in any direc- 
tion you choose by placing the extremity of the red-hot bar a little 
before it. The crack speedily extends to the bar. The bar is then 
withdrawn a little further on. 1n this manner you proceed till you 
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