perfluent

a Spring-water; but that which will Lather with Soap, or such soft water that percolates through Chalk, or a Grey Fire-stone, is generally accounted best, for Chalks in this respect excell all other Earths, in that it administers nothing unwholsome to the perfluent waters, but undoubtedly absorps by its drying spungy Quality any ill minerals that may accompany the water that runs thro 'them.

The London and Country Brewer Anonymous