_Of Wells and Cisterns._
It being remarkt oftentimes that the Water which is under the Earth hath
many bad Qualities, and exhales vapours, which often stifles those which
work in the _Wells_, after that they are dug, & the Water begins to
gather together. The Ancients had this Precaution, to let a Lamp gently
down into it, and if it extinguished it, they took it for an Infallible
sign that the Water was bad.
The _Cisterns_ were made to receive Rain Water in great Conservatories
under Ground, whose Walls on all Sides, and at the bottom were built
with Mortar of strong Lime, and Sand, and Pebbles, all well beaten
together. They made several Conservatories, and the Water passed from
one to another, to the end it might leave all the Dirt in the first and
second; They likewise put Salt in their _Cistern-Water_ to make it more
subtile.