n it for
the reason that this view gives the due proportion of chemical value to
the several contributory treatments--alkaline hydrolyses (caustic lime
and soda boils), hypochlorite oxidations, and incidental acid treatments
(souring). The first of these is by far the largest contributor of
'chemical work,' though the second, by being the agent for the actual
whitening effect or bleaching action proper, occupies a position of
often exaggerated importance.

In bleaching processes there has been no radical change of system on the
large scale since the introduction of the 'Mather' kier in 1885, and the
associated change from lime and ash boiling to the caustic soda
circulating boil with reduced volume of lye, which this mechanical
device rendered practicable. It is outside the scope of this work to
follow up this branch of technology in any detail, and we cannot discuss
the evolution of systems on variations of detail where no essential
principle is involved. But we have to notice a very recent development
which has only just begun its industrial career, and which does give
effect to a principle of treatment not previously applied. This is
tersely stated by its originator, William Mather,[13] in the
expression, 'it is more economical to make liquids pass through cloth
than to make cloth pass through liquids.' The starting point of this
development is the invention of a complete self-contained machine in
which a rolled batch of cloth can receive a succession of chemical
treatments, with accessory washings--the solutions, or wash waters,
being circulated through the cloth. The essential fact on which this
system is based is that a perfect liquid circulation can be maintained
from selvedge to selvedge through the folds of a tightly rolled batch of
cloth. Such circulation is therefore quite independent of the diameter
of the batch. If we consider a cloth under chemical treatment with
solutions, it is clear that the reactions and interchanges of soluble
matters within the cloth, within the twisted elements of the yarn, and
in the last grade of distribution within the actual ultimate fibres, are
subject to capillary transmission, and osmotic exchange. There is a
mixture of these molecular effects, with the circulation in mass,
sweeping both faces of the cloth. It is obvious that for the mass effect
a relatively very small volume of circulating liquid is necessary to
maintain uniform conditions of action. In the actual dispositio