1As it is the opinion of physiologists, philosophers and priests that all things proceed from water, I thought it necessary, as in the preceding seven books rules are laid down for buildings, to describe in this the method of finding water, its different properties, according to the varied nature of places, how it ought to be conducted, and in what manner it should be judged of; inasmuch as it is of infinite importance, for the purposes of life, for pleasure, and for our daily use. This will be easily accomplished if the springs are open and flowing above ground. If that be not the case, their sources under ground are to be traced and examined. In order to discover these, before sunrise one must lie down prostrate in the spot where he seeks to find it, and with his chin placed on the ground and fixed, look around the place; for the chin being fixed, the eye cannot range upwards farther than it ought, and is confined to the level of the place. Then, where the vapours are seen curling together and rising into the air, there dig, because these appearances are not discovered in dry places.
1This will be easier if there are open springs of running water. But if there are no springs which gush forth, we must search for them underground, and conduct them together. The following test should be applied. Before sunrise, lie down flat in the place where the search is to be made, and placing the chin on the earth and supporting it there, take a look out over the country. In this way the sight will not range higher than it ought, the chin being immovable, but will range over a definitely limited height on the same level through the country. Then, dig in places where vapours are seen curling and rising up into the air. This sign cannot show itself in a dry spot.