16. Mention the depth of penetration in case of the 24-pdr. siege-gun. At 100 yards a 24-pdr. ball with a charge of one-third of its weight will penetrate as follows: Feet. Inches. In earth of old parapets, 8 6 “ “ recently thrown up, 15 0 “ Oak wood, sound and hard, 4 6 “ Rubble stone masonry, 1 10 “ Brick, 3 0 17. What is the depth of penetration of field pieces? Fired at the distance of 500 or 600 yards, the penetration will be from 4½ to 6 feet in parapets recently constructed, and will traverse walls of ordinary construction; but a 12-pounder is necessary to make a breach in walls of good masonry and of 4 feet in thickness, and in this case the position of the battery must be favorable, and the operation a slow one. 18. In attacking a post, or fortified position, in what manner should the fire from artillery be carried on? Previous to an assault, the artillery ought to support the other troops by a combined fire of guns, howitzers, and small mortars, so that, if possible, the fire may be simultaneous, as such a diversity of projectiles would tend to distract the defenders and prevent them from extinguishing any fire among buildings, besides throwing them into confusion at the moment of assault. In cases of surprise, when immediate action is required, the above method cannot, of course, be practicable. 19. When firing guns of different calibres at long ranges, what are the probabilities of hitting the object? As the squares of the diameters of their respective shot, when of equal density, and fired with proportional charges. [Sidenote: 151]] PART XIV. MISCELLANEOUS. 1. What is the velocity of sound in the air? At the temperature of 33° the mean velocity of sound is 1100 feet in a second. It is increased or diminished _half a foot_ for each degree of temperature above or below 33°. 2. How can the distance of an object be ascertained by the report of fire-arms? By observing the number of seconds that elapse between the flash and the report of a gun, and multiplying the number by the velocity of sound in the air. 3. What is momentum? The force possessed by a body in motion; and is measured by the product of the mass of the body into its velocity. 4. When equal masses are in motion, what proportion do their momenta bear to their velocities? They are proportional to their velocities. 5. When velocities are equal, what proportion do their momenta bear to their masses? They are proportional to their masses. 6. What proportion do the momenta bear to each other when neither the masses nor velocities are equal? They are to each other as the products of their masses into their velocities respectively. 7. What is the average weight of a horse? About 1000 pounds. [Sidenote: 152]] 8. What space does a horse occupy in the ranks; in a stall; and at a picket?