FUZES.
Principle of operation.—We have just learned something of the force of inertia in connection with a projectile. Most fuzes are actuated by this force. From our knowledge of the trajectory we know that usually a projectile does not strike on its nose. Therefore we cannot devise our fuzes to work like the driving of a nail into a board. The striking element is the anvil and is a fixed pointed spur against which a sliding element containing a fulminate strikes. The sliding block carries a small charge of black powder which is set off by the fulminate, thus igniting the train which leads to the high explosive charge detonator. Were this sliding block left free to slide back and forth at all times it would be unsafe to transport the fuze, as it might be set off by accident. There must be therefore some means of holding it safely away from the anvil until it is desired to detonate the charge. There are thus two conflicting conditions to be met: safety during transportation and sensitiveness at the point of departure. It may not be understood at first why sensitiveness at the point of departure should be a condition to be met. Suffice it to say that all fuzes are designed to arm at discharge or soon after leaving the bore for they must be ready to act at any time after leaving the muzzle. Were they to be safe during flight they might be so safe that the remaining velocity would not be sufficient to set them off. All fuzes are designed to arm as we say either during travel through the bore or immediately after.