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When I bought this funny looking
lamp from a junk dealer at Wimborne Market I thought it was a
Miners' Lamp but I've now discovered it was used in sewers to
detect gas. I don't know why this is needed as I imagined that
all sewers are filled with gas anyway but presumably it's used
as a means of letting the chaps that visit such places that the
level of gas is too high for safety?
Click
the lamp to see a bigger picture
The Spiralarm has the maker's name J.H.NAYLOR,
WIGAN and has Type "S" marked on the label. I understand
the Type "M" was used in mines and has a slightly different
characteristic so that the gas type and percentage that it detects
is different.
The patent number is given on the label
as 352267.
http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=GB352267&F=0
reveals the patent details, from which
can be seen that the design dates to 1931. I should think that
my model is rather later than that, but I shall leave that to
experts in the matter.
Operation is relatively simple. In the
presence of an inflammable gas in the surrounding air the flame
gets bigger and heats a bimetal strip which operates a set of
contacts, turning on a lamp in the lower compartment.
The materials from which the lamp is
chiefly constructed are aluminium (or one of its more robust
alloys), and brass.
As you can see a spare wick is looped
around the base.. in fact it's possible that the lamp has never
been used and the original? wick never fitted.
Clipped onto the base is a mirror made
from chrome plated steel.
A knurled brass adjuster is located
underneath the base. This presumably to enable the flame height
to be preset and to allow for wick to be raised when it's burned
down. |
