623 
winning the coal has taken precedence of the graver question 
of ventilation. Hence the almost universal practice of 
placing the winnings on the dip, or lowest portion of the 
field ; which serves the mechanical convenience of extracting 
the coal, both as regards its drainage and underground 
transit ; but in the matter of ventilation, is directly opposed 
to the selection of such a point, as would be^t facilitate the 
free escape of explosive gases from the mine. 
In every coal mine there must be " goaf," or chasms from 
which the coal has been exhausted ; and it is to the quiescent 
abode presented by these spaces, and the apertures and cavi- 
ties in the roof above them, that the more dangerous gases 
resort ; escaping by their undisturbed seclusion, admixture 
with the circulating current which would otherwise effect 
their expulsion. 
In the history of colliery explosions, it has rarely, if ever 
happened, that the true cause of mischief has been thoroughly 
and conclusively probed and understood. The presence of 
gas in an inflammable condition is manifest, but whether as 
the result of a sudden disclosure of what is termed a "blower/' 
or the stealthy invasion of the goaf- secreted enemy, conse- 
quent upon a change of barometrical pressure, the fall of 
roof, concussion of air, or other contingency, remains a 
problem of undefined and unfathomable mystery. 
At the door of this treacherous foe the mischief has long 
been laid ; and to the unavoidable presence of " goaf," and 
the dangers inseparable from its existence, on present systems 
of ventilation, we chiefly owe the invention and use of the 
several forms of that humane instrument, known as the 
" Safety Lamp." Far be it from us to underrate the value 
and good service which have been rendered by this important 
invention. A retrospect of our mining experience does, how- 
ever, justify us in the inquiry, whether the " Safety Lamp " 
has in reality been a blessing or the reverse ? That its use 
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