It varies from 15 to 23 calibres. 5. What proportion does the dispart of a gun bear generally to its length? About a sixtieth part in field guns, about a thirtieth part in sea-coast, and about a thirty-eighth part in siege and garrison guns. 6. What is the natural angle of sight in siege and garrison guns? One degree and thirty minutes. 7. What is it in field guns? One degree. 8. Why have sea-coast guns no natural line of sight? Because the swell of the muzzle is not visible when the eye is on a level with the base ring. 9. Upon what are guns mounted? On field, siege, barbette or casemate carriages. [Sidenote: 27]] 10. What projectiles are used with guns? Solid shot, spherical case, grape, and canister. 11. About what are the weights of the different guns? 6-pdr., 884 lbs.; brass 12-pdr., 1,757 lbs.; iron 12-pdr., 3,590 lbs.; 18-pdr., 4,913 lbs.; 24-pdr., 5,790 lbs.; 32-pdr., 7,200 lbs.; 42-pdr., 8,465 lbs. 12. Give the entire length of the several guns? 6-pdr. field-gun, 65.6 inches; 12-pdr. field-gun, 85 inches; 12-pdr. iron gun, 116 inches; 18-pdr., 123.25 inches; 24-pdr., 124 inches; 32-pdr., 125.2 inches; 42-pdr., 129 inches. [Sidenote: 28]] PART I. SECTION III. ON HOWITZERS. 1. What is a _Howitzer_? A chambered piece, of larger calibre than a gun of like weight, and mounted in a similar manner. 2. What form of chamber is given to howitzers? That of a cylinder. 3. How is it united with the large cylinder of the bore? By a conical surface, except in the 8-inch siege howitzer, where it is united with the cylinder of the bore by a _spherical_ surface, in order that the shell may—when necessary—be inserted without a sabot. 4. What advantages are gained by the employment of howitzers? They project larger shells than the guns with which they are associated, are well adapted for ricochet fire, the destruction of field works, breaking down palisades, and setting fire to buildings. 5. What projectiles are used with howitzers? Shells usually, spherical case, canister, grape and carcasses. [Sidenote: 29]] 6. Give the entire length of the several howitzers. Iron 10-inch, 124.25 inches; 8-inch sea-coast, 109 inches; 8-inch siege and garrison, 61.5 inches; 24-pdr. garrison, 69 inches; 32-pdr. field, 82 inches; 24-pdr. field, 71.2 inches; 12-pdr. field, 58.6 inches; mountain, 12-pdr., 37.21 inches. 7. What is the weight of a howitzer of each kind? 10-inch, 9,500 lbs.; 8-inch sea-coast, 5,740 lbs.; 8-inch siege and garrison, 2,614 lbs.; 24-pdr. garrison, 1,476 lbs.; 32-pdr. field, 1,920 lbs.; 24-pdr. field, 1,318 lbs.; 12-pdr. field, 788 lbs.; 12 pdr. mountain, 220 lbs. 8. What is the natural angle of sight in siege and garrison and field howitzers? One degree. 9. What in mountain howitzers? Thirty-seven minutes. 10. Why have sea-coast howitzers no natural line of sight? Because the swell of the muzzle is not visible when the eye is on a level with the base ring. [Sidenote: 30]] PART I. SECTION IV.