omposition. The cartridges were wrapped in paper saturated with
paraffin-wax, and afterwards dipped in hot paraffin to secure their being
water-tight. The Miners' Safety Explosives Co., when making this explosive
at their factory at Stanford-le-Hope, Essex, abandoned after a short trial
the above composition, and substituted di-nitro-naphthalene 11.5 per cent.
for the mono-nitro-naphthalene, and used thin lead envelopes filled with
loose powder slightly pressed in, in place of the compressed cylinders
containing loose powder. The process of manufacture is shortly as
follows:--132-3/4 lbs. of thoroughly dried nitrate of ammonium is placed
in a mill pan, heated at the bottom with live steam, and ground for about
twenty minutes until it becomes so dry that a slight dust follows the
rollers; then 17-1/2 lbs. of thoroughly dry di-nitro-naphthalene is added,
and the grinding continued for about ten minutes. Cold water is then
circulated through the bottom of the pan until the material appears of a
lightish colour and falls to powder. (While the pan is hot the whole mass
looks slightly plastic and of a darker colour than when cold.) A slide in
the bottom of the pan is then withdrawn, the whole mass working out until
the pan is empty; it is now removed to the sifting machine, brushed
through a wire sieve of about 12 holes to the inch, and is then ready for
filling into cartridges. The hard core is returned from the sifting
machine and turned into one of the pans a few minutes before the charge is
withdrawn.

The ammonite is filled into the metallic cartridges by means of an
archimedian screw working through a brass tube, pushing off the cartridges
as the explosive is fed into them against a slight back pressure; a cover
is screwed on, and they then go to the dipping room, where they are dipped
in hot wax to seal the ends; they are then packed in boxes of 5 lbs. each
and are ready for delivery. The di-nitro-naphthalene is made at the
factory. Mono-nitro-naphthalene is first made as follows:--12 parts of
commercial nitrate of soda are ground to a fine powder, and further ground
with the addition of 15 parts of refined naphthalene until thoroughly
incorporated; it is then placed in an earthenware pan, and 30 parts of
sulphuric acid of 66 deg. B. added, 2 parts at a time, during forty-eight
hours (the rate of adding H_{2}SO_{4} depends on the condition of the
charge, and keeping it in a fluid state), with frequent agitation, day and