1816.] On Lighting Coal Mines. 119 
should render it impossible to form these channels of connexion 
with established air shafts, a new air shaft should be formed to com- 
mand the upward air-drainage of the new workings. Might not 
this be effected, and the number of up-air shafts be considerably 
increased without exceptionally deforming the upper surface of the 
soil, by ascertaining above by trigonometrical calculation the point 
from which descending a new shaft might be established ; and might 
not such shafts be formed by an improved precess in boring and 
letting down iron pipes to preserve and'to keep open the: shaft? 
If, in boring, any considerable quantity of water should be pierced, 
more than can easily be disposed of (the great objection to air 
shafts), as the boring would be from the top of the surface, no 
harm would ensue, and the boring on that point might be aban- 
doned. 
The heavy, or azotic and carbonic acid gases, can only be ren- 
dered innoxious by ventilation and mixture with,atmospheric air 
introduced from above by currents established by mechanical means 
through shafts and channels passing to the very bottom of the mine, 
or by giving directions to the currents produced by various causes 
within the mine itself. ; 
These mechanical means of discharge are applicable to these 
gases as noxious to human life generally, and undoubtedly they are 
the great and direct means to be resorted to for these purposes. 
The insufficiency of these means always to discharge the light gas, 
its explosibility, the necessity of using fires to give light in the dark 
abysses of the earth, and the difficulty of ascertaining when and 
where the dangerous accumulations thereof exist, have rendered it 
a desirable thing to discover, if possible, any mechanical con- 
trivance by which the benefit of light may be obtained without the 
danger of fire. 
' Two of the plans recommended for the purpose will be consi- 
dered: that which in times past has been invented, and continues 
to be now used, of obtaining light by the collision of flint and 
steel; and that which in the present day has been proposed by Sir 
Humphry Davy, and is now before the public, of a closed lantern, 
the passage of air through which is duly regulated. 
The use of flint and steel does not seem to be sufficiently under- 
stood in its principles. That it is not secure against explosions is 
admitted ; and I am inclined to think that the dependance upon, 
and safety expected from, its use, isin a great measure illusory. 
Whenever it has produced explosion, it is not doubted that the 
flame of a taper would have produced it. Would the flame of a 
taper produce it where the collision does not? Jam inclined to 
think that the light in fire, for such it is, produced by these colli- 
sions, fails to fire air not explodible, and fails not to fire explodible 
air. 
If the collision of flint and steel be made in vacuo at the points of 
contact, and there only, light is exhibited; when the collision is made 
in atmospheric air, the abraded portions of steel fly off in a high state 
