56 ON THE FIRE-DAMP OF COAL-MINES, 
it, a lantern of this kind can be made to project light in a 
straight line to a great extent, and illumination may be thrown 
into a passage, or along the side of a wail which is to be work- 
ed, by its being placed at one extremity. This may not only 
have the advantage of economy, but of greater safety, so as te 
render this method proper to be employed on this account 
alone, independent of any other consideration ; for the lamp 
being placed at some distance from the miner, the risk is 
avoided from the concussion arising from his working, from 
any fall from the roof, or from the sudden discharge of the in- 
flammable gas from any opening in the coal. Iumination 
may also be thus obtained, in situations where, from imperfect 
ventilation, it is difficult to support the combustion of a lamp, 
such as the close extremities of passages or of new workings. 
These are the very places, too, which are more peculiarly liable 
to the accumulation of the inflammable air; and in both re- 
spects, therefore, the advantage is obvious, of a mode by 
which, where the direction of the working admits of it, (which 
it will almost always do to a certain extent,) light may be 
thrown from a distant spot, where the same difficulty and the 
same hazard do not exist. Lastly, In ascertaining the state of 
the air in passages where danger is suspected, or in exploring 
them after the accident of an explosion, the same method will 
give greater safety. Where a more diffused light is wanted, 
this is easily attained by the surface of the lens being more or 
less scratched. 
Note E. page 45.—When the workings of a mine are car- 
ried to a considerable distance from the course of the current 
of air, without a corresponding shaft being made, the ventila- 
tion becomes very imperfect. In this case, it is stated in a ve- 
ry candid communication by Mr Scort, (Edinburgh Journat, 
December 
