Laboratory, Royal. An extensive military manufacturing department in Woolwich Arsenal, England. Although it has existed for many years, it was only in 1855 that the present very large establishment was organized. Here are foundries for the casting of shot, shell, grape, etc.; apparatus for the manufacture of percussion-caps, which are formed—hundreds at a time—out of the copper sheet; presses where rifle-bullets are squeezed into shape; fuzes in all stages of manufacture; and a thousand other instances of combined ingenuity and power. The British government grants permission to inspect the factory. There are also laboratories—though on a comparatively small scale—at Portsmouth and Davenport, England.
Laboratory Stores. The following are among the laboratory stores used in service:
The [time-fuze], the [percussion-fuze], and the [concussion-fuze] (which see).
The wooden fuze consists of a conical plug of wood of the proper size for the fuze-hole of the shell with which it is to be fired. The axis of this plug is bored out cylindrically from the large, down to within a short distance of the small end, which is left solid. At the large end a cup is hollowed out, and the outside of the plug is divided into inches and parts, generally tenths, commencing at the bottom of the cup. The cylindrical space is filled with composition, pounded hard, and as regularly as possible, and the cup filled with meal powder moistened with whisky or alcohol. The rate of burning is determined by experiment, and marked on a waterproof cap, which is tied over the cup. Knowing the time any shell is to occupy in its flight, the fuze is cut off with a saw at the proper division, and firmly set in the fuze-hole with a fuze-set and mallet. The disadvantage of this fuze is its irregularity, it being very difficult to pound the composition so that equal lengths will burn equal times. The shell may either burst too soon, and a great part of its effect lost, or it may burst after burying itself in the ground, or it may burst after passing the proper point. This irregularity of burning is common to all fuzes where the composition is driven in successive layers in a column which burns in the same direction. This fuze is used with mortar shells. The composition of mortar-fuzes is, nitre 2 parts, sulphur 1 part, and meal powder 3 parts; the quantities of meal powder vary in fuzes for mortars of different calibers. Generally these fuzes are cut before being inserted in the shell; but they are sometimes bored through at the proper positions instead of being sawed. They are also cut obliquely, when the fuze is so long as to render it likely that it will reach the bottom of the shell; for by cutting it perpendicular to the axis, the whole base of the wood might be driven in contact with the bottom of the shell, and prevent the lighted composition from setting fire to the bursting charge.
The paper time-fuze consists of a cylindrical column of burning composition packed in a paper case, gradually increasing in thickness from its lower to its upper or outer extremity; to insure ignition, it is primed with rifle-powder at the larger end. It is inserted at the time of loading the piece into a brass or wooden plug previously driven into the fuze-hole of the shell. The composition has the same ingredients as gunpowder, the proportions being varied to suit the required rate of combustion; pure meal powder gives the quickest composition; by adding certain proportions of sulphur and nitre, the composition burns more slowly. The rate of burning also depends upon the density of the composition and the purity and thorough mixture of the ingredients. These fuzes vary in length, burning from 4 to 40 seconds; they are graduated in seconds on the outside of the case, and can be cut to a length corresponding to any intermediate time of flight.
Belgian, or Bormann-fuze. See [Bormann-Fuze].
The Wright-fuze, a modification of the Bormann-fuze, extends the time of burning to 12 or 14 seconds.
United States sea-coast fuze. The paper case fits in a fuze-plug of bronze instead of wood. It fits the fuze-hole of the shell in the same way as the wooden plug, and is retained by the force of friction. A safety-cap and primer combined have been adopted to prevent ricochets, especially over water, from extinguishing the fuze. A recess in the top, filled with priming composition, is covered until the fuze is required for use, with a disk of lead or paper fitting accurately the opening. The fire is conveyed to the fuze composition through a crooked passage which is filled with priming, and prevents water from entering in sufficient quantity to extinguish the fuze. For security a small leaden plug is placed in the inner end of the fuze-plug, where it remains until it is driven out by the shock of the explosion. When the shell is placed in the piece, nothing more is necessary than to remove the disk which covers the recess in the top. Paper-fuzes are inserted at the moment of loading the gun, and into wooden or brass fuze-plugs previously driven into the shell.
Port-fire consists of a small paper case, filled with a highly inflammable but slow-burning composition, the flame of which is very intense and penetrating, and cannot be extinguished by water, it is principally used as an incendiary material in loading shells, and for communicating fire to the priming of guns when proving them.
Port-fire composition consists of nitre, sulphur, and meal powder, in different proportions. One kind is composed of nitre, 65 parts; sulphur, 22.5 parts; and meal-powder, 12.5 parts. A port-fire case, 18 inches in length, filled with this composition, burns 10 minutes.