days' fighting because we were brought to a standstill through want of ammunition," occasional consignments of 18-pounder long cases at Crewe grew less and less until they finally ceased altogether, being thereafter superseded by the shorter cases of the 4·5-inch high-explosive shell, which, as time went on, were showered on the Works in ever-increasing quantities; in fact, a total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 60 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 they (the walls of the case) are slightly tapered to within about 1/2 inch of the mouth which fits parallel over the end of the shell. [Illustration: ROLLING OUT DENTS IN 4·5-INCH FIRED CARTRIDGE CASE. [_To face p._ 89.]