e bleaching agent which
has previously passed through the other chests of the series, as will
be hereinafter described, is introduced so that both enter together at
the lower portion of the first chest, _a_, of the series. The said
materials are caused to flow into the chest continuously, so that the
portion at each moment entering tends to displace that which has
already entered, thus causing the materials to rise gradually or flow
upward from the bottom to the top of the chest.

Suitable stirring devices or agitators, _c_, may be employed to keep
the pulp in suspension and to expose it thoroughly and uniformly to
the liquid introduced with it.

[Illustration: Fig. 2]

When the materials (the pulp and the bleaching liquid) arrive at or
near the top of the chest, they are partially separated from one
another and removed from the chest at substantially the same rate that
they are introduced, as follows: Each chest is provided at its upper
part with a liquid conveyor, _d_, having a construction similar to
that of the device known as a "washer" in paper making machinery,
consisting of a rotating drum, the periphery of which is covered with
gauze, which permits the liquid to pass into it, but excludes the pulp
suspended in the liquid, the said drum containing blades or buckets
that raise the liquid which thus enters through the gauze and
discharges it at _d2_ near the axis of said drum. There is one of
these washers in each one of the series of chests, and each discharges
the liquid taken from its corresponding chest into the inlet pipe of
the next preceding chest of the series, the washer in the chest,
_a4_, for example, delivering into the inlet passage, _b_, of the
chest, _a2_, and so on, while the washer of the first chest, _a_,
of the series delivers into a discharge pipe, _e_, through which the
liquid may be permitted to run to waste or conveyed to any suitable
receptacle, if it is desired to subject it to chemical action for the
purpose of renewing its bleaching powers or obtaining the chemical
agents that may be contained within it.

The operation of the washers in removing the liquid from the upper
part of the chest tends to thicken the pulp therein, and the said
thickened pulp is conveyed from one chest to the next in the series by
any suitable conveying device, _f_ (shown in this instance as a worm
working in a trough or case, _f2_), which may be made foraminous
for the purpose of permitting the liquid to dr