294 On the Ventilation of Coal-Mines. [Apriz, 
it will be much easier to find the points wherein they differ than 
those in which they agree. 
It will be perceived, in the first place, that the workings, instead 
of being oblique, are rectangular: and it will immediately occur, 
that on the face of a considerable slope, rectangular workings are 
almost of all other forms the most likely to detain a portion of the 
fire-damp in the lateral branches; while oblique workings are of all 
others the most likely to let it pass upwards. It will next be ob- 
served, that the great object under the present system is to convert 
the whole of the workings into a tube, which winds up and down 
the slope alternately : and which is terminated at one end by the 
downcast shaft, where the atmospheric air enters, and at the other 
by the upcast shaft, where it is discharged. ‘This certainly wears 
an appearance of great simplicity, and could we but forget the 
declination of the strata, and the levity of carbureted hydrogen 
gas, it might be reckoned an admirable contrivance. But neither 
the Felling colliery, nor perhaps any other, is a dead level:: on the 
contrary, it dips at the rate of * one yard in twelve, a declivity 
sufficient to give motion to a loaded waggon, which in its descent 
drags an empty one up the inclined plane, thereby saving the ex- 
pence of many horses. ‘Taking the mean length of these workings 
to be 500 yards, in the direction of the dip and rise, the astonishing 
fact meets us, that, whatever portion of fire-damp may be evolved 
in any one passage, it must, after having actually ascended 125 
feet perpendicular, again descend as many feet; and this repeatedly, 
before it can arrive at the upeast shaft. What are the consequences 
to be expected from this preposterous opposition ‘to the natural 
levity of fire-damp? they are these: that it will resist being carried 
down the slope, with all the powers of doing so with which nature 
has furnished it, which are by no means small; that, though a 
great part certainly may, and must descend, yet it will take all 
opportunities of absconding by the way into the lateral openings; 
that a part of it will always linger in the upper ends of. the pas- 
sages, and in many a corner whence it cannot be dislodged; that, 
in short, it will accumulate in the upper parts of the workings, and 
that it may be expected to explode there. And your readers will 
accordingly find, that the fire-damp in the Felling colliery actually 
exploded in the precise spot, where, from the influence and com- 
bination of the circumstances just enumerated, an explosion was to 
have been expected. Is another proof wanted? a melancholy one 
is at hand. Let your readers refer to an account of a second 
explosion in the same colliery, which is likewise recorded in 
the Annals of Philosophy, vol. iii. p. 132, and which cost the 
lives of 23 persons; and they will find that the fire-damp again 
* P. 33 of the Narrative, and p 442, vol. i, of the Annals. To understand this 
part of Mr, Hodgson’s narrative peifectly, it is necessary to substitute the word 
south-east for the word south-west, which must haye been an error of the press, 
and which has been copied into the Annals, 
