When the jelly in the tanks has become semi-transparent and the cotton has
entirely dissolved, the mixture should be transferred to the mixing
machine. The mixing machines are specially designed for this work, and are
built in iron, with steel or bronze kneading- and mixing-blades, according
to requirements.

A suitable machine for the purpose is that known as the Nito-Universal
Incorporator, shown in Fig. 30, which has been specially constructed by
Messrs Werner, Pfleiderer, & Perkins, Ltd., after many years' experience
in the mixing of explosive materials, and is now almost exclusively
adopted in both Government and private factories. Mr George M'Roberts'[A]
mixing machine, however, which is shown in Fig. 31, is still used in some
factories for dynamite jelly.

[Footnote A: See _Jour. Soc. Chem. Ind._, 1890, 267.]

If it is intended to make gelignite, or gelatine dynamite, it is at this
point that the proper proportions of wood-pulp[A] and potassium nitrate
should be added, and the whole well mixed for at least half an hour, until
the various ingredients are thoroughly incorporated.

[Footnote A: Most of the wood-pulp used in England is obtained from
pine-trees, but poplar, lime, birch, and beech wood are also used. It is
chiefly imported as wood-pulp. The pulp is prepared as follows:--The bark
and roots are first removed, and the logs then sawn into boards, from
which the knots are removed. The pieces of wood are afterwards put through
a machine which breaks them up into small pieces about an inch long, which
are then crushed between rollers. These fragments are finally boiled with
a solution of sodium bisulphite, under a pressure of about 90 lbs. per
square inch, the duration of the boiling being from ten to twelve hours.