‹‹‹ Vitr. 8.6.12 | Table of Contents | Vitr. 8.6.14 ›››
13To avoid this the following method may be adopted; a lighted lamp must be lowered; if it continue to burn, a man may safely descend, but if the strength of the vapour extinguish it, then to the right and left of the well let air holes be dug, so that as it were through nostrils, the vapour may pass off. When this is done and we come to water, the well must be lined with a wall, but in such a manner as not to shut out the springs.
13To guard against this, we must proceed as follows. Let down a lighted lamp, and if it keeps on burning, a man may make the descent without danger. But if the light is put out by the strength of the exhalation, then dig air shafts beside the well on the right and left. Thus the vapours will be carried off by the air shafts as if through nostrils. When these are finished and we come to the water, then a wall should be built round the well without stopping up the vein.