ON COLUMBIADS. 1. What is a _Columbiad_? A gun of much larger calibre than the ordinary gun, used for throwing solid shot or shells. 2. What are some of the peculiarities of this gun, when mounted in barbette? Its carriage gives a vertical field of fire from 5° depression to 39° elevation; and a horizontal field of fire of 360°. 3. Are these pieces chambered? Those of the old pattern have chambers; but they are now cast without any. 4. Give the weight of this piece? 10-inch, 15,400 lbs.; 8-inch, 9,240 lbs. 5. What is the entire length of this gun? 10-inch, 126 inches; 8-inch, 124 inches. 6. What is the natural angle of sight in this piece? 8-inch, 1° 23´; 10-inch, 1° 21´. [Sidenote: 31]] PART I. SECTION V. ON MORTARS. 1. What is a _Mortar_? The shortest piece in service; the trunnions are placed in rear of the vent at the breech; the bore is very large in proportion to the length, and is provided with a chamber. 2. What are the principal advantages obtained by the employment of mortars? Reaching objects by their vertical fire—such as a town, battery, or other place—whose destruction or injury cannot be effected by direct or ricochet fire; dismounting the enemy’s artillery; setting fire to and overthrowing works; blowing up magazines; breaking through the roofs of barracks, casemates, &c.; and producing havoc and disorder amongst troops. 3. What do you mean by vertical fire? That produced by firing the mortar at a high elevation. 4. What are its advantages? The shell having attained a great elevation, descends with great force on the object, in consequence of the constant action of the force of gravity on it. [Sidenote: 32]] 5. Why are mortars constructed stronger and shorter than other pieces? Because greater resistance is required in consequence of the high elevation under which they are fired; and were they longer, the difficulty experienced in loading them would become too great. 6. Why is a mortar constructed with a chamber? In consequence of employing various charges, some very small, it becomes necessary to use a chamber to concentrate the charge as much as possible, so that the shell may be acted on by the entire expansive force of the powder. 7. What form of chamber is given to mortars? Usually that of a frustum of a cone. The bottom is hemispherical in the sea-coast, stone, and eprouvette mortars. In siege mortars it is a plane surface, the angles of intersection being rounded in profile by arcs of circles. 8. What is this form of chamber called? Gomer Chamber. 9. What is the advantage of the conical over the cylindrical chamber? Cylindrical chambers are objectionable, as the projectile is frequently broken in consequence of the small surface exposed to the action of the charge. This defect is obviated by large chambers, and particularly by those that are conical, in which the charge is expended upon nearly a hemisphere. 10. What form of chamber has the eprouvette?