🚀 go-pugleaf

>     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
{ihnp4, hplabs, amdcad, ucbvax!dual}!fortune!stirling

In article <238@sri-arpa.ARPA> JOHNSON%nuhub.acs.northeastern.edu@CSNET-RELAY.ARPA writes:
>
>     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


This is what is called a "DAVEY LAMP". It is named after Humphrey Davey, 
an early scientist. I don't know if he discovered the principle or if he
was just the one to put it to use. I was told that it works due to the 
fact that the metal screen conducts heat away from the gas too fast for
the flame to pass through. This can be demonstrated with a candle and 
some metal window screen. The screen has to be fine enough to do the job,
but still coarse enough to let light through. Marine supply houses sell
"flame screen" to put between the manifold and the carb. to help prevent
stack fires in boats. It is fun to play with. Try puting the flame of a 
butane lighter to a piece of screen and you will find that it won't go 
through. You can also light the gas on the other side of the screen and
it won't get back to the lighter. 

If someone has more information, I would like to hear it too. If my
information is incorrect please let me know (no flames please, I've 
got screen over my CRT so it wouldn't do any good anyway 8-) ).

Hope to hear more.

In article <145@fortune.UUCP> stirling@fortune.UUCP (Patrick stirling) writes:
>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

Right about the lamp, wrong about the inventor:

1) The name was Davy (Sir Humphrey): President of the Royal Society

2) He DIDN'T invent it: it was actually invented (many years before I
seem to remember)
by George Stephenson(sp?) of Stephenson's Rocket and Locomotion fame.
It was known in the north of England as the Geordie Lamp.

A royal commission eventually determined this some while later.
(Although it didn't decide whether he'd stolen it or not!).

This is a classic example of social and professional snobbery:
Davy was an upper-class scientist, while Stephenson was a working class
(unqualified) engineer: guess who got believed initially,
in spite of the fact that the Geordie Lamp had been IN USE for years prior to
Davy's invention (if indeed he did invent it independently).

	Yours angrily (:-),
-- 

		Dave Lukes. (...!inset!dave)

``Fox hunting: the unspeakable chasing the inedible'' -- Oscar Wilde

Yes, the candle works.  If you are ever in Chicago, visit the Museum of
Science and Industry.  Among the exhibits there is a "working" coal mine
that you can take tours through.

At the end they demonstrate the miners lamp.  I recall it had something
other than a candle in it, but all that matters is a flame.  If the wire
mesh around the candle is intact, the flame will flash but will not pass
the screen.  If even a tiny hole exists in the mesh, the mine itself will
explode.  There are boxes at the top of the shaft to test the lamps before
entering the mine.  I believe that they are still used to test for gas
by mine engineers, but the average miner uses electric lights.

Bob Campbell - Hewlett Packard Information Technology Group
	       hpdsd!campbelr@hplabs.HP.COM

> Right about the lamp, wrong about the inventor:
> 1) The name was Davy (Sir Humphrey): President of the Royal Society

Well, having seen 3 different wrong spellings, I can resist no longer.
The name is Sir Humphry Davy!  By the way, if you visit Penzance, you
can see his statue, on the main street just near the railway station.

In article <780001@hpdsd.UUCP> campbelr@hpdsd.UUCP (Bob Campbell) writes:
>At the end they demonstrate the miners lamp.  I recall it had something
>other than a candle in it, but all that matters is a flame.  

Candles burn with a higher temperature and there is all the trouble
with the dripping, running wax.  Gas jet flames were better.  The one 
I had, if memory serves, used Calcium Carbide "stones" and by dripping 
water on them they would generate acelylene gas.  This burns with a 
very smokey flame (lots of radiating surface) and a cup of the stuff 
(fuel) would last for quite a spell (as they used to say). 

Naturally, Union Carbide and Carbon Company made the fuel. 

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>     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

The miners' safety lamp was invented by Sir Humphrey Davy.  It
works because the metal cage conducts the heat away sufficiently
to cool the burning gases below the ignition point, so the flame
cannot get out of the cage.

Incidentally, this still leaves the problem of the miner being
asphyxiated by the coal gas.  An additional feature is that the
candle flame burns bluish when gas is present, which warns the
miners.  Before that, they used canaries (when the canary drops
dead, move out).