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lupton: safety lamps. 
care and skill, of some lamp cleaner who has very little experience. 
For my part I would sooner carry an old Davy lamp than take a 
shielded lamp which I had not seen put together myself unless I had 
the assurance of some pitman that he had seen it put together. It 
has been suggested that safety can be insured by testing the lamps 
in an explosive mixture every day as they are given out. When I 
gave evidence to the Royal Commissioners about six years ago, I 
told them that I did not consider such a system of tests was practic- 
able, and I have seen no reason to alter my opinion. When an im- 
perfect lamp is put in an explosive mixture it may ignite the gas or 
or it may not; the ignition proves the lamp to be bad, but the 
failure to ignite it does not prove the lamp to be good. A means of 
rapidly applying a really searching test, such as a rapid current of 
explosive gas, in a rapid and practical manner, has not yet been 
adopted, and if it is ever adopted it will be a rather costly operation. 
The more common tests of putting the lamp for a few seconds into 
a box filled with an explosive mixture, or passing it through a ring 
of gas jets, are absolutely worthless, and the plan recommended by 
the Commission is very little better. They recommend a vertical 
tube about eight inches in diameter and two feet long open at both 
ends, and gas jets at the bottom, so that there may be a constantly 
ascending current of explosive gas. (See fig. 13.) An imperfect lamp 
put into such a tube may or may not explode the gas; if it does 
not explode nothing it proved at all. To illustrate this I have pre- 
pared a few experiments: — 
1. I take a Clannylamp with a hole in the gauze i inch in 
diameter, manifestly a very unsafe lamp ; I put it into the hole which 
contains an explosive mixture ; the lamp is at once extinguished. 
2. I take a Stephenson lamp with a hole about f inch diameter, 
punched through the copper cap of the glass and through the gauze 
cap, that too is extinguished. 
3. I take a Stephenson lamp and remove the glass, leaving it a 
large Davy, then 1 punch a hole J inch diameter in the side of the 
gauze, that too is extinguished. 
4. Then I take a Shield lamp and omit one of the gauzes, so 
that there is a straight opening entirely unprotected, and put that 
into the explosive mixture, that too goes out. 
