distinctive points deserve to be noticed in the centrifugal used for
this purpose. An endless chain or belt provided with blades moves the
material vertically in the basket, and discharges 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.