harges it over the edge.
During its upward course the material is subjected to a shower of water
to wash it.

OIL FROM METAL CHIPS.--Very material savings are made in many factories
by collecting the metal chips and turnings, coated and mixed with oil,
which fall from the various machines, and extracting the oil
centrifugally. The separator consists of a chip holder, having an
imperforate shell flaring upward and outward from the spindle (in fixed
bearings) to which it is attached. When filled, a cover is placed upon
it and keyed to the spindle. Between the cover and holder there is a
small annular opening through which oil, but not chips, can escape.
Fig. 29 (Pat. 225,949--C.F. Roper) is designed (like the greater part
of the drawings inserted) to show relative position of parts merely,
and not relative _size_. This style of machine can be used for sugar
separating (Pat. 345,994--F.P. Sherman) and many other purposes, to
which, however, there are other styles more especially adapted.

[Illustration: Fig. 29.]

FILTERERS.--There are two distinct kinds of centrifugal filterers,
working on different principles. Petroleum separators (Pat. 217,063)
are of the first kind. They are in form in all respects like a sugar
machine. The flakes of paraffine, stearine, etc., which are to be
extracted, when chilled are very brittle and would be disintegrated
upon being hurled against a plain wire gauze and would escape. Even a
woven fabric presents too harsh a surface. It is necessary to have a
very elastic basket lining of wool, cotton, or other fibrous material.
The basket itself may be either wire or perforated, but must have a
perfectly smooth bottom.

As the pressure of the liquor upon the filtering medium per unit of
surface depends entirely upon its radial depth, mere tubes, connecting
a central inlet with an annular compartment, will serve the purpose
quite as well as a whole basket. In this style of machine (Pat. 10,457)
the filtering material constitutes a wall between two annular
compartments. The outer one is connected with a vacuum apparatus.

Filterers of the second kind work on the following principle: If a
cylinder be rapidly revolved in a liquid in which solid particles are
suspended, the liquid will be drawn into a like rotation and the heavy
particles will be thrown to the outer part of the receptacle. If a
perforated cylinder is used as stirrer, the purified liquid will escape
into it through the perforations