396 
GARFORTH: FIRE-DAMP DETECTOR, 
Safety lamps when first introduced were received with some 
distrust, but after a time the Davy, with apertures of to of 
an inch in diameter, became to be implicitly relied upon, especially in 
a current moving* at a slow velocity. The Davy lamp now exhibited, 
is supposed to be a fac-simile of Sir Humphrey Davy's original lamp, 
the first ever used in a coal mine, and was sent by him, in the early 
part of 1816, to the Rev. John Hodgson, Vicar of Heworth, 
Newcastle-on-Tyne, and afterwards presented by his relatives to the 
School of Mines, in London. This lamp is almost identical with the 
Davy of to-day, the slight difference being in the strength of some of 
the parts, an improvement which any ordinary workman could suggest. 
About the year 1835 the Davy lamp was proved unsafe in an 
explosive current of 6ft. per second, and since that time some of 
our most eminent scientific men have endeavoured to find a safer 
light. The result has been, that more than 100 different patents 
have been taken out. For many years past the writer has been 
endeavouring to discover a Light without a Flame sufficient for 
practical use in the mine. Experiments have been conducted on 
Phosphorus, the Electric Light, and different kinds of safety lamps. 
Without troubling you with the details of such experiments, it may 
perhaps be well to state the danger of applying the Electric light in 
mines. There is an impression that the incandescent lamps (now in 
general use on the surface) might be used with advantage, if sufficient 
electricity could be stored in a portable form, but the objection is that 
if electric wires are allowed to cross each other and then separate, 
an action similar to the effect produced by a fall of the roof, electric 
sparks are emitted by which the gas has been ignited. What is 
required in a mine is not only a light, but an indication to the miner 
that the atmosphere surrounding him is sufficiently pure to breathe. 
The principal requirements of a safety lamp are : — to be so 
sensitive as to indicate at once the presence of gas, by allowing the 
atmosphere to reach the flame without obstruction, and yet so 
shielded as to resist an explosive current moving at a high velocity ; 
that an ample supply of air may be obtained to support combustion, 
and yet have some internal arrangement by which the products of 
an explosion inside the lamp will cause it to be self extinguishing ; 
