i8 Sir Humphry Davy on the fire-damp of coal mines , and on 
Longitudinal air canals of metal may, I find, be employed 
with the same security as circular canals ; and a few pieces 
of tin-plate soldered together with wires to regulate the dia- 
meter of the canal, answer the purpose of the feeder or safe 
chimney, as well as drawn* cylinders of brass. 
A candle will burn in a lantern or glass tube made safe with 
metallic gauze, as well as in the open air ; I conceive, how- 
ever, that oil lamps, in which the wick will always stand at 
the same height, will be preferred. 
But the principle applies to every kind of light, and its 
entire safety is demonstrated. 
• When the fire-damp is so mixed with the external atmo- 
sphere as to render it explosive, the light in the safe lantern 
or lamp will be extinguished, and warning will be given to 
the miners to withdraw from, and to ventilate, that part of 
the mine. 
* J 
If it be necessary to be in a part of the mine where the 
fire-damp is explosive, for the purpose of clearing the work- 
ings, taking away pillars of coal, or other objects, the work- 
men may be lighted by a fire made of charcoal, which burns 
without flame, or by the steel mill, though this does not 
afford such entire security from danger as the charcoal fire. 
It is probable, that when explosions occur from the sparks 
from the steel mill, the mixture of the fire-damp is in the 
proportion required to consume all the oxygene of the air, 
for it is only in about this proportion that explosive mixtures 
can be fired by electrical sparks from a common machine. 
As the wick may be moved without communication between 
the air in the safe lantern or lamp and the atmosphere, there 
is no danger in trimming or feeding them ; but they should be 
