to be dry, i.e., to contain from 0.25 to 0.5 per cent. of moisture. It is
then ready to be sifted. During the process of removing to the sifting
house and the sifting itself, the cotton should be exposed to the air as
little as possible, as dry nitro-cotton absorbs as much as 2 per cent. of
moisture from the air at ordinary temperatures and average dryness.

The drying house usually consists of a wooden building, the inside of
which is fitted with shelves, or rather framework to contain drawers, made
of wood, with brass or copper wire netting bottoms. A current of hot air
is made to pass through the shelves and over the surface of the cotton,
which is spread out upon them to the depth of about 2 inches. This current
of air can be obtained in any way that may be found convenient, such as by
means of a fan or Root's blower, the air being passed over hot bricks, or
hot-water pipes before entering the building. The cotton should also be
occasionally turned over by hand in order that a fresh surface may be
continually exposed to the action of the hot air. The building itself may
be heated by means of hot-water pipes, but on no account should any of the
pipes be exposed. They should all be most carefully covered over with
wood-work, because when the dry nitro-cotton is moved, as in turning it
over, very fine particles get into the air, and gradually settling on the
pipes, window ledges, &c., may become very hot, when the slightest
friction might cause explosion. It is on this account that this house
should be very carefully swept out every day. It is also very desirable
that the floor of this house should be covered with oilcloth or linoleum,
as being soft, it lessens the friction.

List shoes should always be worn in this building, and a thermometer hung
up somewhere about the centre of the house, and one should also be kept in
one of the trays to give the temperature of the cotton, especially the
bottom of the trays. The one nearest to the hot air inlet should be
selected. If the temperature of the house is kept at about 40 deg. C. it will
be quite high enough. The building must of course be properly ventilated,
and it will be found very useful to have the walls made double, and the
intervening space filled with cinders, and the roof covered with felt, as
this helps to prevent the loss of heat through radiation, and to preserve
a uniform temperature, which is very desirable.

The dry cotton thus obtained, if not already fin