274 
LUPTOI^: SAFETY LAMPS. 
one gauze will make a lamp safe, two gauzes would make it safer, and 
three gauzes safer still. It was this form of reasoning which led 
M. Marsaut to improve the Clanny lamp, by putting two gauzes 
instead of one (see figs. 7, 8) and also three gauzes. By this arrange- 
ment the lamp is made perfectly safe for fire-trying, but a shield is 
necessary to make it safe in a rapid current. With a well-constructed 
shield and two gauzes the lamp is probably safe at 1500 feet, with 
three gauzes it has resisted trials at a velocity of 3000 feet, and, I 
believe, 5000 feet. 
In choosing a safety lamp the great weight of authority is in 
favour of having one that gives a good light, and that is, therefore, 
the first consideration. Therefore it is necessary to have: — (1) glass 
lamps, and (2) in order that the lamp may be always in good order, 
the inlet air should not pass through gauze or perforations on a level 
with the oil-pot, therefore the air must enter the lamp above the 
glass. Gauze or perforations at the oil-pot level are sure to get 
clogged and dirty. (3) The colliers and deputies ought to be able to 
see that all the essential parts of the lamp are in their proper place 
before it goes into the mine, and for that reason the shield should be 
removed after using, and before the lamp is given out again it should 
be examined by the collier and a deputy before the shield is attached. 
It has always been considered essential in using safety lamps, that 
they should be examined by the collier and by the fire-man or deputy, 
and any departure from this rule involves greater risks by far than 
those now incurred by the use of the common Davy. (4) The lamp 
should be so designed that when it is put together for use, it cannot 
be partially opened, without undoing the lock ; a great many of the 
glass lamps in common use are so made that the glass can be loosened 
so as to entirely destroy the safety of the lamp, and this may be done 
inadvertently. 
Before proceeding further, it may be well to consider the electric 
light, and it must be admitted that if we are seeking a perfect lamp 
in order to avoid a risk that may not occur in any mine for thirty 
years, we must at once regard as inadmissible any light in a mine 
that causes additional risk. No gas lamp, or any other lamp than 
the best safety lamp should go below the pit bank, or be within reach 
