A hole was drilled in the face of the tunnel, and the charge inserted.

Then all retreated back into the Tomb of Kings till the cartridge had exploded, and the smoke cleared off, which took a long while, when our people advanced with iron bars and baskets, and cleared away the debris, after which the process must be repeated.
Oh! the heat of that narrow hole deep in the bowels of the rock, and the reek of the stagnant air which sometimes was so bad that the lights would scarcely burn.

Indeed, after a hundred feet had been completed, we thought that it would be impossible to proceed, since two men died of asphyxiation and the others, although they were good fellows enough, refused to return into the tunnel.

At length, however, Orme and Japhet persuaded some of the best of them to do so, and shortly after this the atmosphere improved very much, I suppose because we cut some cranny or shaft which communicated with the open air.
There were other dangers also, notably of the collapse of the whole roof where the rock was rotten, as we found it to be in places.

Then it proved very hard to deal with the water, for once or twice we struck small springs impregnated with copper or some other mineral that blistered the feet and skin, since every drop of this acid water had to be carried out in wooden pails.