_Second._--Suppose for a particular range the dimension, say height of the 50-per-cent zone, is given in the range table as 4 feet, and we wish to know what percentage of shots will probably strike a zone 7.6 feet high. If we divide 7.6 by 4, we obtain 1.9, and from the table we see that the factor 1.9 corresponds to 80 percentage. Therefore we may assume that 80 per cent of the shots at that particular range will probably strike a zone 7.6 feet high. For all practical purposes we may consider that the factor of the 80-per-cent zone is 2, of the 95-per-cent zone is 3, and of the 100-per-cent zone is 4. SHELL. A shell is a hollow projectile containing a bursting-charge of gunpowder, or some high explosive, and a fuze to ignite the charge at some point of its flight, or on impact. Its penetration into earth at 850 yards may be taken at 12 to 15 feet for field-guns. It is invariably fired with a percussion-fuze, and is used against material. SHRAPNEL. A shrapnel consists of a collection of lead balls in an envelope, and bearing a small bursting-charge, which, by action of the fuze, ruptures the envelope at some point of the projectile's flight, and leaves each bullet free to describe its own path, and the paths thus described, taken together, form the _cone of dispersion_. [Illustration: FIG. 106.] TIME-SHRAPNEL. This shrapnel is used entirely against animate objects, its main purpose being to cover a given area with a powerful and effective bullet-fire, and must have, at the instant it bursts, a terminal velocity of 500 ft.-sec. to be effective. The trajectory of shrapnel until it bursts is identical with that of shell. On its bursting the bullets spread in every direction, and form a cone of more or less denseness. This cone will increase in size as the range increases, because the velocity of translation decreases more rapidly than the velocity of rotation. On the other hand, the area of the oval formed by the intersection of this cone with the ground will decrease as the angle of fall increases. This oval has its greatest depth in the direction of fire, and its broadest end furthest away from the gun. Its depth diminishes as the range increases, and for short ranges it is much greater than for long ones. The breadth increases as the distance short of the object at which the burst takes place increases. The nearest bullet (that is, the one which has travelled the shortest distance) will have the highest striking velocity, and the bullet that travels furthest will have the lowest striking velocity, the bullets between striking with proportionate velocities. As the distance short of the object at which the shell bursts increases so will the distances between the bullets on striking increase. [Illustration: _Actual Intersection of Sheaf._ FIG. 107.]