of shots at one time. The waggons are then advanced, and the débris is cleared away; the two pairs of rails at the sides, shown in the cross section, are for 
LONGITUDINAL SECTION OF THE END OF THE ADVANCED GALLERY.waggonets, whose contents are afterwards transferred to large waggons. The "affût" is then again advanced. These operations are now repeated
with unvarying regularity twice every day.
The temperature at the working face of the advanced gallery is seldom higher than from 75° to 76°, and the atmosphere is as pure as can be desired, when the machines are at work.[1] This, it must be remembered, is notwithstanding the presence of more than thirty men,[2] and almost as many lamps, in a space about nine feet wide, eight high, and fifty long. The comparative lowness of the temperature is of course due to the expansion of the compressed air.
At the distance of a hundred and sixty paces, the sound of the machines could not be distinguished, and the atmosphere again gradually deteriorated as we approached the region which may, not improperly, be termed infernal. Once more we passed through the foul vapours and by the army of miners. Laborious as the work of these men undoubtedly is, it is lighter and far less dangerous than that of our coal-cutters. The heat, although it seems considerable to one coming from a lower temperature, is not excessive, and this may be inferred from seeing how few men
- ↑ The temperature is raised to 80° or 86° after the mines are exploded.
- ↑ 1 chef; 4 machinists; 2 master miners, who determine the direction of the holes; 8 labourers, who guide the boring-rods; 9 workmen, who look after the perforatrices; 5 boys; 8 labourers; 2 workmen, who keep up communication with the exterior,—in all, 39 persons.
