290 On the Ventilation of Coal-Mines. [ApRIL, 
So long, then, as there is only the passage B, C, D, between the 
two shafts, the ventilation of this passage is an operation of great 
simplicity ; but this passage is only the base line, as it may be called, 
from which numerous excavations are to proceed in different direc- 
tions, as far as the right of working extends, or as far as it may be 
possible to carry them with safety. Hence it is obvious that, as the 
space thus hollowed out below ground enlarges, the atmospheric 
eurrent ought to flow through every part of the workings, to enable 
the workmen to breathe, to supply air for the necessary quantity of 
light, and to prevent the fire-damp from stagnating in dangerous 
quantities. 
To give your readers an idea of the mode in which this may be 
effected, Fig. 2 represents a ground plan of the cval-field, of which 
Fig. 1 isa perpendicular section. In this figure, B is the downcast, 
or lower shaft ; D, the wpcast, or higher shaft ; and C, the passage 
connecting them, as already shown in Fig. 1. The shaded rhom- 
boidal figures are the pillars or masses of solid coal, left standing to 
support the roof ; and the parallel and oblique openings between the 
pillars are the workings, or excavations, left empty by removing the 
coal; and through which an adequate supply of atmospheric air 
must be constantly directed, to ensure the safety of the mine. 
It is a fact well known, and particularly by miners, that the cur- 
rent of atmospheric air in a mine will, when unobstructed, always 
take the most direct passages it can find, from its entrance to its 
outlet. Hence the direction of this current when introduced at B, 
the downcast shaft, would be along the passage C, to the upeast 
shaft at D. This, however, would not answer the purpose of ven- 
tilating the other parts of the mine; but if we stop the passage C 
at or near to the shaft B, we shall turn the current into the two 
next passages, e, e, on each side of B. If we want to carry it 
further, it is only necessary to stop the passages, e, e, and then will it 
proceed to the next pessages, f, f, and so on, by similar means, to 
the extremities of the workings, g, g. To distribute this current 
equally the shaft B may be divided by a partition across it; but in 
practice it will be found to divide itself accurately, in proportion to 
the demand opened for it. 
It is not, however, to be understood, that the whole of the cir- 
culating current is to be introduced into any one passage, unless on 
some very particular occasions. In the ordinary circumstances of 
the mine, it must be carefully distributed through all the passages 
by a judicious application of séoppings; and these must be so con- 
structed as to admit the necessary supply of air to the passages in 
which they may be placed. ; 
Nothing can answer so well fora stopping as a door, hung on 
hinges from the roof, so as to swing freely in either direction, and 
so placed, that, when at rest in its perpendicular position, it may 
accurately shut up the passage, It is obvious, that by opening such 
a door more or less, the current of air through the passage in which 
it stands may be regulated at pleasure; and that it may be fixed at 
