348 Mr. Buddle's Narrative of the Explosion
ascertained that it requires fourteen or fifteen volumes of atmospheric air to dilute one volume of the carburetted hydrogen of our collieries below the point of explosion. It, therefore, follows, that to place any colliery in a safe working state, requires fourteen or fifteen times as much atmospheric air
to be passed through the workings, as they produce of gas. But this is not all, this current of air must be carried through every part of the mine where gas is to be found, so as to prevent accumulations; otherwise, no current of air, however, powerful, would render the workings safe from explosion. It is the impossibility of preventing such accumulations of gas, in collieries working pillars which renders them more liable to heavy explosions.
The first step towards the ventilation of a colliery is, to introduce a powerful current of atmospheric air into it. The next is to regulate and conduct that current into the several workings and ramifications of the mine as circumstances may require. I shall only state, in this place, the various means by which the former is effected, as the latter will be explained in
the sequel.
The ventilation of mines is sometimes effected by the natural operation of the atmosphere; as, for example, when two pits are situated upon different surface levels, the rise of the ground being more than the rise of the seam between them, as represented in the diagram. In this case the top of the Pit A being lower than the top of the Pit B, supposing the atmosphere to be in a quiescent state, and the temperature of the air to be
