The cavity left in the amatol by the tube of the extruding machine is filled with molten T. N. T., and a cavity is produced in this T. N. T. into which the booster fits. This is necessary in order to provide for complete detonation. The booster cavity is produced either by the use of a former, which upon removal leaves a cavity of the proper size, or by plunging the booster into the shell filling before this is cooled, or by drilling out a cavity for the booster after the filling has been thoroughly cooled. A large number of rounds of ammunition of all calibers had also to be loaded with a flashless compound that was inserted in the propelling charges, so that the discharge of the guns would not betray their positions to the enemy at night, while a smoke compound was inserted in a large quantity of shell so that each missile of this character might be located after firing to determine the accuracy of the shot. Coordination of manufacture of metallic parts so as to cause the proper quantities of shell, fuse, and boosters to be produced without leaving any incomplete rounds that would have to be held awaiting other components caused the greatest difficulty. The magnitude of the task of providing the necessary shell components in the tremendous quantities required can be better appreciated by a realization of the fact that the various parts of each component must be made to fit each other properly and perfectly. Gauging had to be resorted to frequently in the process of manufacture to make certain that there was perfect interchangeability of parts of each component to prevent any waste of time in selecting parts to fit each other. The complete components, too, must themselves be made with equal care and scrupulous attention to make certain that they fit properly. Thus, the booster had to be made in such a fashion and with such precision and accuracy that it would fit perfectly into the shell as well as into the booster cavity in the shell filling into which it is screwed and also at the same time accommodate the fuse which screws into the booster. This extreme accuracy made necessary a large number of gauges, which had to be designed at the same time as, and in coordination with, the design of the component. For example, in a complete round of artillery ammunition, 80 dimensions must be gauged. To standardize the gauges used for these 80 dimensions, 180 master gauges are required, while the actual number of different gauges used during the various stages of manufacture of a complete round is over 500. Government inspectors required over 200 gauges in their work of inspecting and gauging the finished components for the shell, so in all about 800 gauges were used in the process of manufacturing a complete round of artillery ammunition, to insure interchangeability of parts, proper fit for the projectile in the gun, and perfect functioning of the various parts. [Illustration: LOADING SMOKELESS POWDER.