GARFOETH : FIRE-DAMP DETECTOR. 397 
to be SO small as not to be an encumbrance in getting through the 
small roadways or places to be examined, (also to prevent the force 
of an explosion inside the lamp bursting the gauze,) and yet so 
arranged that it will burn for 8 or 10 hours without getting too 
hot ; to be so light that it may be carried for hours without diflSculty, 
and yet so strong as to resist a certain amount of rough usage ; to 
give a good light, not only to enable the miner to get the coal, but 
to enable him to see the breaks in the roof (it has been stated there 
are more accidents from falls of roof, on account of the poor light 
given off by the Davy or Stephenson, than with the candle.) 
The comparative lighting power of some of the principal lamps 
now in use is as follows : — 
English Standard sperm candle burning 120 grains per hour 100 
Improved Mueseler 70 
Davy 37 
Stephenson 20 
The writer succeeded about three years ago in constructing a 
lamp unlike any existing one, which fulfilled many of the before 
mentioned requirements, but as it was dependant on the movement 
of a small fan to obtain and regulate the supply of air, it could not 
be recommended for daily use, as some of the parts were liable to 
derangement owing to the dust in the mine. As an instance of 
the difficulty of obtaining a perfectly safe light, it may be stated 
that recently a prize of £500 was offered by Mr. Ellis Lever, and 
108 different lamps competed, but no lamp fulfilled the conditions 
ordinarily required in a mine, and the prize was not awarded. 
During the last few years, and based on a great number of 
experiments and trials, several improvements have been made in the 
lamp, the most important being the Mueseler Chimney and the Tin 
Shield. The object of the chimney is to throw back the carbonic 
acid gas (the result of the explosion inside the lamp) on to the flame 
and so extinguish the light. With a properly constructed chimney 
where all the space can be filled with carbonic acid gas, the flame of 
the lamp, in an explosive current of 19 feet per second, is extinguished 
before firing the gas outside. Above that velocity, and with the 
current du-ected to the upper part of the internal chimney, the flame 
can be drawn (somewhat on the principal of the Injector) to the top 
