Works in ever-increasing quantities; in fact, a total of close on two million had been dealt with when the All-Highest finally "threw up the sponge" and accomplished his memorable "bunk" into Holland. To pick a cartridge case up and look at it, one would say that there was literally nothing in it; yet on second thoughts it is surprising what a number of features are embodied in its hollow and simple form. It is solid drawn, of a substance the colour of brass called yellow metal, which is composed of 6 per cent. electrolytic copper and 40 per cent. zinc, and which costs actually £25 per ton less than brass. The base is integral and thick, with an external rim, behind which a clip automatically engages as the breech of the gun closes, for the purpose of extracting the case after the gun is fired. Into a hole in the centre of the base is screwed the percussion cap, which acts virtually in the capacity of a "sparking plug" to the gun, differing only from the familiar petrol-engine sparking plug, in that the spark which fires the propellant charge inside the cartridge case is created, not by the break of an electric current, but by the sudden shock or percussion of a striker against a cap in which is contained a thin, albeit highly explosive layer of fulminic acid and gunpowder. The walls of the case are thin, thereby expanding against the walls of the breech of the gun, and preventing any escape of the propellent gases; and for the purpose of easy extraction SEQUENCE OF OPERATIONS 89 they (the walls of the case) are slightly taper to within about inch of the mouth which fits parallel over the end of the shell. Upon receiving a returned, or fired, cartridge case in the Works, the primer is first of all removed, then the case is boiled in a solution of caustic soda for the purpose of removing grease and dirt. What is known as a "hardness" test follows next in order of sequence, this to determine whether the metal of the case is still good for further service, and is performed by a little instrument known as a sclerometer (derived, as our classical contemporaries will tell us, from the Greek word σkλýpos, hard), consisting of a tube marked with a graduated scale down which a tiny metal ball is dropped on to the side of the case; the ball should rebound to a point on the scale approximating a height of two inches, anything below this proving that the metal has become too soft for further use, when the case is accordingly scrapped. The cases which show a requisite degree of hardness are then annealed or suitably tempered round the mouth, this process ensuring a subsequent loose fit round the end of the shell. Rolling the mouth to internal limit gauges is effected by means of a specially improvised apparatus rigged up on the bed of an engine lathe, consisting of two fixed housings inside which runs a belt-driven sleeve bored to the correct taper of the cartridge case, and in which the latter is carried. A duplex ball-bearing roller running on a central spindle secured in a |