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From: stirling@fortune.UUCP (Patrick Stirling)
Newsgroups: sci.physics
Subject: Re: coal mines and candles
Message-ID: <145@fortune.UUCP>
Date: Fri, 7-Nov-86 13:56:40 EST
Article-I.D.: fortune.145
Posted: Fri Nov  7 13:56:40 1986
Date-Received: Sat, 8-Nov-86 18:44:45 EST
References: <238@sri-arpa.ARPA>
Reply-To: stirling@fortune.UUCP (Patrick stirling)
Organization: Fortune Systems, Belmont, CA
Lines: 20

>     At one time I was informed that early coal miners used candles on 
>their helmets to provide light in the mines.  This would cause an 
>explosion now and them because of coal gas build-up.  Someone 
>discovered that by putting a metal cage around the flame, the candle 
>could be safely used in the mine.
>     Does anybody know whether or not this is true, who discovered it 
>and why it works?
>Chris Johnson
>Northeastern University

I'm 'F'ing instead of 'r'ing beacuse I don't think your return path
will work. 
I dimly recall from school that the lamp was called a 'Davies safety Lamp',
presumably invented by Davies (!). It worked, I think, on the principle
that the metal shield would conduct heat well enought to prevent the
flame front of the burning bas from getting through the shield. The lamp 
also worked as a coal gas indicator - when there was coal gas present,
the candle flame had a blue (I think) aura.
patrick
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