es to the introduction of small oil-lamps. In the less fiery
mines on the Continent, oil-lamps of the well-known Etruscan pattern are
still in use, whilst small metal lamps, which can conveniently be
attached to the cap of the worker, occasionally find favour in the
shallower Scotch mines. These lamps are very useful in getting the coal
from the thinner seams, where progress has to be made on the hands and
feet. At the close of the last century, as workings began to be carried
deeper, and coal was obtained from places more and more infested with
fire-damp, it soon came to be realised that the old methods of
illumination would have to be replaced by others of a safer nature.

It is noteworthy that mere red heat is insufficient in itself to ignite
fire-damp, actual contact with flame being necessary for this purpose.
Bearing this in mind, Spedding, the discoverer of the fact, invented what
is known as the "steel-mill" for illuminating purposes. In this a toothed
wheel was made to play upon a piece of steel, the sparks thus caused
being sufficient to give a moderate amount of illumination. It was found,
however, that this method was not always trustworthy, and lamps were
introduced by Humboldt in 1796, and by Clanny in 1806. In these lamps the
air which fed the flame was isolated from the air of the mine by having
to bubble through a liquid. Many miners were not, however, provided with
these lamps, and the risks attending naked lights went on as merrily as
ever.

In order to avoid explosions in mines which were known to give off large
quantities of gas, "fiery" pits as they are called, Sir Humphrey Davy in
1815 invented his safety lamp, the principle of which can be stated in a
few words.

If a piece of fine wire gauze be held over a gas-jet before it is lit,
and the gas be then turned on, it can be lit above the gauze, but the
flame will not pass downwards towards the source of the gas; at least,
not until the gauze has become over-heated. The metallic gauze so rapidly
conducts away the heat, that the temperature of the gas beneath the gauze
is unable to arrive at the point of ignition. In the safety-lamp the
little oil-lamp is placed in a circular funnel of fine gauze, which
prevents the flame from passing through it to any explosive gas that may
be floating about outside, but at the same time allows the rays of light
to pass through readily. Sir Humphrey Davy, in introducing his lamp,
cautioned the miners against expo