It is a spherical shell having three additional holes, of the same dimensions as the fuze-hole, pierced at equal distances apart in the upper hemisphere of the shell, and filled with a composition which burns with intense power from eight to ten minutes, and the flame issuing from the holes, sets fire to everything combustible within its reach; it is used in bombardments, setting fire to shipping, &c.; and is projected from cannon like a common shell. 12. What is a substitute for a carcass? Common shells loaded in the following manner: The bursting charge is placed in the bottom of the shell in a flannel bag, over which carcass composition is driven until the shell is nearly filled; then insert four or five strands of quick-match, which must be secured by driving more composition upon it. These shells, after burning as a carcass, explode. 13. What is a fire-ball, and its use? It is a projectile of an oval shape, formed of sacks of canvas filled with combustible composition, which emits a bright flame. Its use is to light up the enemy’s works, and it is loaded with a shell to prevent it from being approached. 14. What is a light ball? Light balls are the same as fire balls, except that there is no shell in them, as they are used for lighting up our own works. [Sidenote: 93]] 15. What is a smoke ball? A hollow paper sphere similar to a light ball, and filled with a composition which emits a dense, nauseous smoke; it is employed to suffocate the enemy’s miners when at work, or to conceal one’s own operations; it burns from twenty-five to thirty minutes. 16. In field pieces to what is the projectile attached? To a block of wood called a sabot. 17. Are the projectile and cartridge ever attached to the same sabot? Yes, in field guns, and the 12-pr. field-howitzer; the whole then constitutes a _round of fixed ammunition_. 18. What is the arrangement in case of the 32 and 24-pdr. field howitzers? The projectile is separate from the charge, and the _cartridge_ is attached to a block of wood called the _cartridge-block_, the object of which is to give a finish to the cartridge and fill the chamber. 19. What difference is there in sabots for field service? Sabots for shot, and spherical case for guns, have one _groove_ for attaching the cartridge—those for gun canisters and for the 12-pdr. howitzer shells, spherical case, and canisters, have _two grooves_. Those for the 32 and 24-pdr. howitzers have no grooves; but are furnished with handles made of cord, passing through two holes in the sabot, and fastened by knots on the inside. 20. How are projectiles for field service fastened to the sabot? By straps of sheet-tin, or of _strong canvas_, when tin or sheet iron cannot be procured. [Sidenote: 94]] 21. How many straps are employed, and how are they fastened?