LUPTON: SAFETY LAMPS. 
275 
of the mine-air issuing from the upcast top. Therefore the incan- 
descent electric lamp for lighting the porch of the downcast bottom 
and the upcast pit top, if coal is wound at the upcast, is a great im- 
provement upon gas or paraffin lamps, because the light is in a 
perfectly air-tight case and no gas can touch it. 
The incandescent electric lamp fulfils all the conditions of a 
perfect lamp ; it is destroyed the instant it ceases to be perfect. 
Perfect as the lamp is, there is a sensible risk in taking it a yard 
beyond the arching of the porch, because the wires that connect it 
with the dynamo are a source of danger. If a wire breaks there is a 
spark, and this would ignite the gas if there was' any; and it is 
doubtful if there is any advantage in the electric light in the porch 
to compensate for the risk incurred through the conducting wires. 
For lighting the working-places of a coal mine a portable lamp 
only is permissable, several of these have been made varying from 
3lbs. to 6lbs. in weight. The 6lb. lamp made by Swan is charged 
by a dynamo on the bank for a small cost, and it is probable 
that the only practical objection to some such lamp is the weight ; 
for a colHer who stops all day in one place this is not serious, but for 
deputies, managers, and horse drivers, it is a serious objection, and 
one that will prevent the general adoption of the 6lb. lamp. The 
3lb. lamp has not yet been made to work cheaply, a cost of chemicals 
alone amounting to one penny a shift is a prohibitory charge. The 
inventors, however, promise to work it for one farthing a shift. For 
the present, therefore, the portable electric lamp is only in the experi- 
mental stage, and the colliery manager of to-day must use a different 
lamp. To-morrow, or next year, the portable electric lamp may be 
perfected. 
As soon as we depart from the older types of lamp we encounter 
new risks; with a Davy lamp we know where we are, we can see if 
the lamp is in proper condition or not, and if it is well made 
it is perfectly safe, except under conditions which very rarely arise, 
but with the new lamps unless a man has seen it put together he 
cannot tell what he is carrying; it might be a lamp without a gauze, 
it might be no safety lamp at all, and the man who enters the most 
dangerous parts of the mine may be trusting entirely to the memory, 
