backwater

It's a volume for those who delight in exploring the backwaters of nineteenth-century opera.

The back-water (overflow) can be used for "thinning down" the chests when emptying. If "Wastive" does this, his mind will be at ease regarding waste of pulp, and his machine-men will be happy and do their work much better than by trying to use all the back-water on the paper machine.