Rapids and Reach

Stones under the columns tune the course of a Confluence: rapids hurry the distillate, a reach spares it and calms the altar. A rapids stone goes under a column: distillate flows faster — three parts a second with four stones — but the streams churn harder.

A reach stone is the opposite: distillate flows slower, down to one part a second, but less of it is needed, up to a fifteenth less, and the altar is calmer. Stones of different kinds cancel each other.