been entirely abandoned, the washing
or "scouring" being effected with soap, assisted by ammonia, potash,
soda or silicate of soda. The finest qualities of wool are washed with
soft soap and potash, while for inferior qualities, cheaper detergents
are employed. The operation is in principle perfectly simple, the wool
being submerged in the warm soap solution, where it is moved about with
forks and then taken out and allowed to drain. A second treatment in
weaker soap serves to complete the process. In dealing with large
quantities, wool-washing machines are employed, which consist
essentially of long cast-iron troughs which contain the soap solution.
The wool to be washed is fed in at one end of the machine and is slowly
propelled to the other end by means of a system of mechanically-driven
forks or rakes. As it passes from the machine, it is squeezed through a
pair of rollers. Three such machines are usually required for efficient
washing, the first containing the strongest and the third the weakest
soap.

The washing of wool is in the main a mechanical process, in which the
water dissolves out the suint while the soap emulsifies the yolk and
thus removes it from the fibre. The attendant earthy impurities pass
mechanically into the surrounding liquid and are swilled away.

In some works the wool is washed first with water alone, the aqueous
extract thus obtained being evaporated to dryness and the residue
calcined. A very good quality of potash is thus obtained as a
by-product. In many works in Yorkshire and elsewhere, the dirty soap
liquors obtained in wool-washing are not allowed to run to waste, but
are run into tanks and there treated with sulphuric acid. The effect of
this treatment is to decompose the soap, and the fatty acids along with
the wool-grease rise as a magma to the surface. The purified product is
known in the trade as "Yorkshire grease."

Attempts have been made from time to time to extract the natural grease
from wool by means of organic solvents, such as carbon bisulphide,
carbon tetrachloride, petroleum spirit, &c., but have not met with much
success.

Worsted yarn spun on the English system, as well as woollen yarn and
fabrics made from them, contain oil which has been incorporated with the
wool to facilitate the spinning. This oil must be got rid of previous to
bleaching, and this is effected by scouring in warm soap with or without
the assistance of alkalis.

The actual bleaching of woo