to the supply of gas by opening or shutting a three-way cock between the
gas generator and the revolving cylinder. This process is assisted by
the use of an exhauster of the usual construction. When fully saturated,
the fabric is allowed to remain until the vegetable fibers are
sufficiently friable. The treatment _in vacuo_ is as follows:

The hydrochloric acid gas passes into a vessel of suitable material
provided with a perforated false bottom. From under this false bottom
a pipe connects with a second similar vessel connected itself with a
vacuum pump having a let-off pipe. As soon as the maximum vacuum is
attained, the gas is turned on through a three-way cock at a pressure of
40 mm. mercury. The gas fills the first vessel and saturates the cloth.
The warmth set free (about 500 calories per kilo, gas) is taken up
by the combined water in the wool, as, owing to the low pressure, a
quantity of vapor is formed sufficient to take up the heat. This vapor
streams through the second vessel at a temperature of 35 deg. Cent.,
penetrates the material, and passes out through the pump. After
saturating the contents of the first vessel the gas passes into the
second. AS soon as this is one-quarter or one-third saturated the first
vessel is taken out and replaced by a third, which receives the overplus
from No. 2 in like manner, and so on. This plan of working prevents gas
passing through and damaging the pump. Instead of working under reduced
pressure, the desired low temperature can be maintained by passing
alternately with the gas currents of air which absorb heat in
evaporating the moisture of the material. The cloth, after saturation by
these processes, is left from six to twelve hours in the vessels, after
which it is freely exposed to the air until the vegetable particles
are friable. As soon as this occurs, the fabrics are washed. It is
advantageous to add to the wash water powdered carbonate of baryta,
strontia, magnesia, or preferably lime, and subsequently to rinse in