a predetermined position both vertically and longitudinally, and
the charge so fixed in its containing case that the centre of gravity
cannot shift. The difficulty of ensuring this with a large torpedo charge
built up from a number of discs and segments is well known. Even with
plain cylindrical or prismatic charges a marked saving in the process of
production is effected by this new system. The charges being in one block
they are more easily handled for the usual periodical examination, and
they do not break or chafe at the edges, as in the case of discs and cubes
in built-up charges. A general view of the press is given in Fig. 19. The
gun-cotton in a container is placed on a cradle fixed at an angle to the
press. The mould is swivelled round, and the charge pushed into it with a
rammer, and it is then swivelled back into position. The mould is made up
of a number of wedge pieces which close circumferentially on the enclosed
mass, which is also subjected to end pressure. Holes are provided for the
escape of water.

[Illustration: FIG. 19.--A 4-CWT. BLOCK OF GUN-COTTON BEING TAKEN FROM
HYDRAULIC PRESS.]

~The Waltham Abbey Process.~--At the Royal Gunpowder Factory, Waltham
Abbey, the manufacture of gun-cotton has been carried out for many years.
The process used differs but little from that used at Stowmarket. The
cotton used is of a good quality, it is sorted and picked over to remove
foreign matters, &c., and is then cut up by a kind of guillotine into
2-inch lengths. It is then dried in the following manner. The cotton is
placed upon an endless band, which conducts it to the stove, or drying
closet, a chamber heated by means of hot air and steam traps to about
180 deg. F.; it falls upon a second endless band, placed below the first; it
travels back again the whole length of the stove, and so on until
delivered into a receptacle at the bottom of the farther end, where it is
kept dry until required for use. The speed at which the cotton travels is
6 feet per minute, and as the length of the band travelled amounts to 126
feet, the operation of drying takes twenty-one minutes. One and a quarter
lb. are weighed out and placed in a tin box; a truck, fitted to receive a
number of these boxes, carries it along a tramway to a cool room, where it
is allowed to cool.

~Dipping.~--Mixed acids are used in the proportion of 1 to 3, specific
gravity nitric acid 1.52, and sulphuric acid 1.84. The dipping tank is
made of cast iron