y pipes is much more
wholesome than that which is conducted through lead pipes, because lead
is found to be harmful for the reason that white lead is derived from
it, and this is said to be hurtful to the human system. Hence, if what
is produced from it is harmful, no doubt the thing itself is not
wholesome.

11. This we can exemplify from plumbers, since in them the natural
colour of the body is replaced by a deep pallor. For when lead is
smelted in casting, the fumes from it settle upon their members, and day
after day burn out and take away all the virtues of the blood from their
limbs. Hence, water ought by no means to be conducted in lead pipes, if
we want to have it wholesome. That the taste is better when it comes
from clay pipes may be proved by everyday life, for though our tables
are loaded with silver vessels, yet everybody uses earthenware for the
sake of purity of taste.

12. But if there are no springs from which we can construct aqueducts,
it is necessary to dig wells. Now in the digging of wells we must not
disdain reflection, but must devote much acuteness and skill to the
consideration of the natural principles of things, because the earth
contains many various substances in itself; for like everything else, it
is composed of the four elements. In the first place, it is itself
earthy, and of moisture it contains springs of water, also heat, which
produces sulphur, alum, and asphalt; and finally, it contains great
currents of air, which, coming up in a pregnant state through the porous
fissures to the places where wells are being dug, and finding men
engaged in digging there, stop up the breath of life in their nostrils
by the natural strength of the exhalation. So those who do not quickly
escape from the spot, are killed there.

13. To 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.

14. But if the ground is hard, or if the veins lie too deep, the water
supply must be obtained from roofs or higher ground, and collected in
cisterns of "signinum work." Signinum work is made as follows. In