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 A slide in the bottom of the pan is then withdrawn, the whole mass working out until the pan is empty; it is now removed to the sifting machine, brushed through a wire sieve of about 12 holes to the inch, and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 The hard core is returned from the sifting machine and turned into one of the pans a few minutes before the charge is withdrawn.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 night, during the first three or four days, afterwards three or four times a day.  In all fourteen days are occupied in the nitration process.  It is then strained through an earthenware strainer, washed with warm water, drained, and dried.  For the purpose of producing this material in a granulated condition, which is found more convenient for drying, and further nitrification, it is placed in a tub, and live steam passed through, until brought up to the boiling point (the tub should be about half full), cold water is then run in whilst violently agitating the contents until the naphthalene solidifies; it can then be easily drained and dried.  For the further treatment to make di-nitro-naphthalene, 18 parts of nitro-naphthalene are placed in an earthenware pan, together with 39 parts of sulphuric acid of 66 deg.  B., then 15 parts of nitric acid of 40 deg.  B. are added, in small quantities at a time, stirring the mixture continually.  This adding of nitric acid is controlled by the fuming, which should be kept down as much as possible.  The operation takes ten to twelve days, when 100 times the above quantities, taken in kilogrammes, are taken.  At the end of the nitration the di-nitro-naphthalene is removed to earthenware strainers, allowed to drain, washed with hot water and soda until all acid is removed, washed with water and dried.  The di-nitro-naphthalene gives some trouble in washing, as some acid is held in the crystals which is liable to make its appearance when crushed.  To avoid this it should be ground and washed with carbonate of soda before drying; an excess of carbonate of soda should not, however, be used.