up through it from a basin below. It is usual to let the milk enter
under hydrostatic pressure (Pat. 239,900--D. M. Weston) and let the
force of expulsion of the cream be dependent on this pressure. This
renders the escape quiet, and prevents churning. Gravity, too, is made
effective in carrying the constituents off.

The cream may escape through a passage in the bottom at the center, and
the skim milk at the lower outer corner; or by ingeniously managed
passages both may escape at or near center. The rate of discharge can
be managed by regulating the size of opening of exit passages.

A curious method consists in having discharge pipes provided with
valves and floats at their lower ends, dipping into the liquid (Pat.
240,175). "The valves are opened and closed, or partially opened or
closed, by the floats attached to them, these floats being so
constructed and arranged with reference to their specific gravity and
the specific gravity of the component parts of the liquids operated
upon, that they will permit only a liquid of a determinate specific
gravity to escape through the pipes to which they are respectively
attached."

We may have tubes directed into the different strata with cutting
edges. (Pat. 288,782.) A remarkable fact noticed in their use is that
these edges wear as rapidly as if solids were cut instead of liquids.

The separated fluids may be received into recessed rings, having
discharge pipes, the proportionate quantity discharged being regulated
by the proximity of the discharge lips to the surface of the ring, and
the centrifugal force being availed of to project the liquids through
the discharge pipes.