unt of
water. It is therefore very desirable that the goods be freed from as
much of this water as possible before they are sent into any drying
chambers, and this may be done in three ways, by wringing, squeezing
and hydro-extracting. The first two methods have already been
described (pp. 198, 199) and need not again be alluded to, the last
needs some account.

[Illustration: Fig. 29.--Hydro-extractor.]

Hydro-extractors are a most efficient means for extracting water (p. 207)
out of textile fabrics. They are made in a variety of forms by several
makers. Essentially they consist of a cylindrical vessel with
perforated sides, so constructed that it can be revolved at a high
speed. This vessel is enclosed in an outer cage. The goods are placed
in the basket, as it is termed, and then this is caused to revolve; at
the high speed at which it revolves centrifugal action comes into play
and the water contained in the goods finds its way to the outside of
the basket through the perforations and so away from the goods.
Hydro-extractors are made in a variety of sizes and forms, in some the
driving gear is above, in others below the basket, in some the driving
is done by belt gearing, in others a steam engine is directly
connected with the basket. Figures 29 and 30 show two forms which are
much in use in the textile industry. They are very efficient and
extract water from textile goods more completely than any other means,
as will be obvious from a study of the table below.

[Illustration: Fig. 30.--Hydro-extractor.]

The relative efficiency of the three systems of extracting the
moisture out of textile fabrics has been investigated by Grothe, who
gives in his _Appretur der Gewebe_, published in 1882, the following
table showing the percentage amount of water removed in fifteen
minutes:--

Yarns. Wool. Silk. Cotton. Linen. (p. 208)
Wringing 44.5 45.4 45.3 50.3
Squeezing 60.0 71.4 60.0 73.6
Hydro-extracting 83.5 77 81.2 82.8

Pieces.
Wringing 33.4 44.5 44.5 54.6
Squeezing 64.0 69.7 72.2 83.0
Hydro-extracting 77.8 75.5 82.3 86.0

In the practical working of hydro-extractors it is of the utmost
importance that the goods be carefully and regularly laid in the
basket, not too much in one part and too little in another. Any
unevenness in this respect at the spe