118 On Lighting Coal Mines. {Fer 
sketched, a copy taken, and, together with the following observa- 
tions, awaited the judgment of the public upon that invention, as 
it might be declared or expressed in one or other of our two philo- 
sophical journals. In No. 36 of Thomson’s Annals for Dec. 1815, 
a lantern constructed by Dr. Murray, of Edinburgh, upon the 
same principle as this, of supplying itself with air from the bottom 
of the mine, is announced as having been exhibited and put ina 
course of trial. Although before the Ist of December, therefore, 
I had never heard of, and have as yet never seen, any representation 
of Dr. M.’s lantern, yet to him, repeating without any malignity of 
imprecation, the prefixed motto, amended from the adage “ pereant 
qui ante nos nostra discerint,” I resign the honour of prior disco- 
very, and, which is of more importance, of future. practical appli- 
cation. 
The figure of the lantern shows its use. It receives the supply of 
air with which it burns exclusively from the bottom of the pit, 
through the flexible tube of leather, covering a spiral wire, and 
terminated by the perforated, globe of metal at its lower extremity, 
which may drag along the ground, whilst the miner carries the 
Jantern, or lie stationary upon it, when the light is stationary. This 
invention was suggested by the following observations, which may 
not be undeserving of notice, although the lantern of Dr. M, pre- 
cede in existence, and be preferred in use. 
Coal-mines are infested with two sorts of noxious airs, differing 
essentially from each other in all their properties. The one, called 
by the miners the choak-damp, the azote and carbonic acid gases of 
chemical philosophy, is heavier than atmospheric air; the other, 
called fire-damp by the miners, the carbureted hydrogen gas of 
chemists, is lighter than atmospheric air. Of course the places 
occupied by each are the bottom and the top, the floors and roofs, 
of mines. Of these gases the former become less and less noxious 
in proportion to their commixture with atmospheric air; the latter 
more and more dangerous, and liable to explosion, in proportion to 
the same commixture, in quantities limited to six parts and 12 
parts of atmospheric air. No commixture of these different noxious 
gases will explode. 
These various properties of these gases indicate the modes to be 
pursued to discharge them from mines, and to destroy their noxious 
qualities. ‘The light air can be, and is, fired with safety, and con- 
sumed as it issues from the crevices of the mine before it mixes 
itself with the atmospheric air in proportions capable of exploding. 
But beyond all question the best and most direct mode of getting 
rid of it is to conduct it with as little agitation as possible, and mix- 
ture with the air of the mine, along the roofs of the mine or channels 
of intersection cut therein, to which in the original workings of 
the mine, and at all times afterwards, a due degree of inclination 
should be given for the purpose, to conduct it to up-air shafts, at 
which it would regularly and safely be discharged. Wherever the 
workings of the mine by irregularity of rise or elevation of root 
