those that do not. A sample of the
calcined guhr should not contain more than 0.5 per cent. of moisture and
organic matter together.

After the guhr is dry it requires to be sifted and crushed. The crushing
is done by passing it between iron rollers fixed at the bottom of a cone
or hopper, and revolving at a moderate speed. Beneath the rollers a fine
sieve should be placed, through which the guhr must be made to pass.

The kieselguhr having been dried, crushed, and sifted, should be packed
away in bags, and care should be taken that it does not again absorb
moisture, as if it contains anything above about five-tenths per cent. of
water it will cause the dynamite made with it to exude. The guhr thus
prepared is taken up to the danger area, and mixed with nitro-glycerine.
The nitro-glycerine used should be quite free from water, and clear, and
should have been standing for a day or two in the precipitating house. The
guhr and nitro-glycerine are mixed in lead tanks (about 1-1/2 foot deep,
and 2 to 3 feet long), in the proportions of 75 of the nitro-glycerine to
25 of the guhr, unless the guhr is found to be too absorbent, which will
cause the dynamite to be too dry and to crumble. In this case a small
quantity of barium sulphate, say about 1 per cent., should be added to the
guhr. This will lessen its absorbing powers, or a highly absorptive sample
of guhr may be mixed with one of less absorptive power, in the proportions
found by experiment to be the best suited to make a fairly moist dynamite,
but one that will not exude.

The mixing itself is generally performed in a separate house. In a series
of lead-lined tanks the guhr is weighed, placed in a tank, and the nitro-
glycerine poured on to it. The nitro-glycerine may be weighed out in
indiarubber buckets. The whole is then mixed by hand, and well rubbed
between the hands, and afterwards passed through a sieve. At this stage
the dynamite should be dry and powdery, and of a uniform colour.

It is now ready to be made up into cartridges, and should be taken over to
the cartridge huts. These are small buildings surrounded with mounds, and
contain a single cartridge machine. Each hut requires three girls--one to
work the press, and two to wrap up the cartridges. The cartridge press
consists of a short cylinder of the diameter of the cartridge that it is
intended to make. Into this cylinder a piston, pointed with ivory or
lignum vitae wood, works up and down from a spring